Chemistry is a branch of physical science that studies the composition, structure and change of matter. Chemistry is sometimes called the science because it bridges other natural sciences, including physics. For the differences between chemistry and physics see comparison of chemistry and physics, the history of chemistry can be traced to alchemy, which had been practiced for several millennia in various parts of the world. The word chemistry comes from alchemy, which referred to a set of practices that encompassed elements of chemistry, philosophy, astronomy, mysticism. An alchemist was called a chemist in popular speech, and the suffix -ry was added to this to describe the art of the chemist as chemistry, the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία and this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, which is in turn derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian.
Alternately, al-kīmīā may derive from χημεία, meaning cast together, in retrospect, the definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term chymistry, in the view of noted scientist Robert Boyle in 1661, in 1837, Jean-Baptiste Dumas considered the word chemistry to refer to the science concerned with the laws and effects of molecular forces. More recently, in 1998, Professor Raymond Chang broadened the definition of chemistry to mean the study of matter, early civilizations, such as the Egyptians Babylonians, Indians amassed practical knowledge concerning the arts of metallurgy and dyes, but didnt develop a systematic theory. Greek atomism dates back to 440 BC, arising in works by such as Democritus and Epicurus. In 50 BC, the Roman philosopher Lucretius expanded upon the theory in his book De rerum natura, unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments.
Work, particularly the development of distillation, continued in the early Byzantine period with the most famous practitioner being the 4th century Greek-Egyptian Zosimos of Panopolis. He formulated Boyles law, rejected the four elements and proposed a mechanistic alternative of atoms. Before his work, many important discoveries had been made, the Scottish chemist Joseph Black and the Dutchman J. B. English scientist John Dalton proposed the theory of atoms, that all substances are composed of indivisible atoms of matter. Davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current, british William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. The inert gases, called the noble gases were discovered by William Ramsay in collaboration with Lord Rayleigh at the end of the century, thereby filling in the basic structure of the table.
Organic chemistry was developed by Justus von Liebig and others, following Friedrich Wöhlers synthesis of urea which proved that organisms were, in theory
Empiricism is a theory that states that knowledge comes only or primarily from sensory experience. It is one of several views of epistemology, the study of human knowledge, Empiricism in the philosophy of science emphasizes evidence, especially as discovered in experiments. Empiricism, often used by scientists, says that knowledge is based on experience. One of the epistemological tenets is that sensory experience creates knowledge, empirical research, including experiments and validated measurement tools, guides the scientific method. The term was used by the Empiric school of ancient Greek medical practitioners, a central concept in science and the scientific method is that it must be empirically based on the evidence of the senses. Both natural and social sciences use working hypotheses that are testable by observation, philosophical empiricists hold no knowledge to be properly inferred or deduced unless it is derived from ones sense-based experience. This view is contrasted with rationalism, which states that knowledge may be derived from reason independently of the senses.
For example, John Locke held that knowledge could be arrived at through intuition. Similarly Robert Boyle, a prominent advocate of the experimental method, the main continental rationalists were advocates of the empirical scientific method. Vaisheshika darshana, founded by the ancient Indian philosopher Kanada, accepted perception and this is enumerated in his work Vaiśeṣika Sūtra. The notion of tabula rasa connotes a view of mind as a blank or empty recorder on which experience leaves marks. This denies that humans have innate ideas, the image dates back to Aristotle, What the mind thinks must be in it in the same sense as letters are on a tablet which bears no actual writing, this is just what happens in the case of the mind. These notions contrasted with Platonic notions of the mind as an entity that pre-existed somewhere in the heavens. This idea was developed in ancient philosophy by the Stoic school. Stoic epistemology generally emphasized that the mind starts blank, but acquires knowledge as the world is impressed upon it.
The doxographer Aetius summarizes this view as When a man is born, such as Sextus of Chaeronea, would continue this idea of empiricism in Stoic writings as well. As Sextus contends For every thought comes from sense-perception or not without sense-perception, so the immaterial active intellect, separate from any individual person, is still essential for understanding to occur. A similar Islamic theological novel, Theologus Autodidactus, was written by the Arab theologian and physician Ibn al-Nafis in the 13th century, during the 13th century Thomas Aquinas adopted the Aristotelian position that the senses are essential to mind into scholasticism
Japanese economic miracle
The Japanese economic miracle was Japans record period of economic growth between post-World War II era to the end of Cold War. During the economic boom, Japan rapidly became the second largest economy by the 1960s. In the Lost Decade of the 1990s, however, it suffered its longest economic stagnation since World War II and this economic miracle was the result of post-World War II Japan and West Germany benefiting from the Cold War. It occurred chiefly due to the economic interventionism of the Japanese government and partly due to the aid, after World War II, the U. S. established a significant presence in Japan to slow the expansion of Soviet influence in the Pacific. This economic miracle was spurred mainly by Japanese economic policy, in particular through the Ministry of International Trade, the Japanese financial recovery continued even after SCAP departed and the economic boom propelled by the Korean War abated. The Japanese economy survived from the recession caused by a loss of the U. S. payments for military procurement.
By the late 1960s, Japan had risen from the ashes of World War II to achieve an astoundingly rapid, the Ministry of International Trade and Industry was instrumental in Japans post-war economic recovery. According to some scholars, no other governmental regulation or organization had more impact than MITI. The particular speed and consequences of Japanese economic growth, established in 1949, MITIs role began with the Policy Concerning Industrial Rationalization that coordinated efforts by industries to counteract the effects of SCAPs deflationary regulations. In this way, MITI formalized cooperation between the Japanese government and private industry, the Ministry coordinated various industries, including the emerging keiretsu, toward a specific end, usually toward the intersection of national production goals and private economic interests. MITI boosted the security by untying the imports of technology from the imports of other goods. MITIs Foreign Capital Law granted the power to negotiate the price.
This element of control allowed it to promote industries it deemed promising. The low cost of imported technology allowed for industrial growth. Productivity was greatly improved through new equipment and standardization, MITI gained the ability to regulate all imports with the abolition of the Economic Stabilization Board and the Foreign Exchange Control Board in August 1952. Power over the foreign exchange budget was given directly to MITI. MITIs establishment of the Japan Development Bank provided the private sector with low-cost capital for long-term growth, the Japan Development Bank introduced access to the Fiscal Investment and Loan Plan, a massive pooling of individual and national savings. At the time FILP controlled four times the savings of the worlds largest commercial bank, with this financial power, FILP was able to maintain an abnormally high number of Japanese construction firms
Ecology is the scientific analysis and study of interactions among organisms and their environment. It is a field that includes biology, geography. Ecology includes the study of interactions that organisms have with other, other organisms. Ecosystems are composed of dynamically interacting parts including organisms, the communities make up. Ecosystem processes, such as production, nutrient cycling. These processes are sustained by organisms with specific life history traits, which refers to the varieties of species and ecosystems, enhances certain ecosystem services. Ecology is not synonymous with environment, natural history and it is closely related to evolutionary biology and ethology. An important focus for ecologists is to improve the understanding of how biodiversity affects ecological function, Ecology is a human science as well. For example, the Circles of Sustainability approach treats ecology as more than the environment out there and it is not treated as separate from humans. Organisms and resources compose ecosystems which, in turn, maintain biophysical feedback mechanisms that moderate processes acting on living and non-living components of the planet, the word ecology was coined in 1866 by the German scientist Ernst Haeckel.
Ecological thought is derivative of established currents in philosophy, particularly from ethics and politics, ancient Greek philosophers such as Hippocrates and Aristotle laid the foundations of ecology in their studies on natural history. Modern ecology became a more rigorous science in the late 19th century. Evolutionary concepts relating to adaptation and natural selection became the cornerstones of modern ecological theory, the scope of ecology contains a wide array of interacting levels of organization spanning micro-level to a planetary scale phenomena. Ecosystems, for example, contain abiotic resources and interacting life forms, an ecosystems area can vary greatly, from tiny to vast. A single tree is of consequence to the classification of a forest ecosystem. Several generations of a population can exist over the lifespan of a single leaf. Each of those aphids, in turn, support diverse bacterial communities, biodiversity describes the diversity of life from genes to ecosystems and spans every level of biological organization.
The term has several interpretations, and there are ways to index, characterize
Physics is the natural science that involves the study of matter and its motion and behavior through space and time, along with related concepts such as energy and force. One of the most fundamental disciplines, the main goal of physics is to understand how the universe behaves. Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy, Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the mechanisms of other sciences while opening new avenues of research in areas such as mathematics. Physics makes significant contributions through advances in new technologies that arise from theoretical breakthroughs, the United Nations named 2005 the World Year of Physics. Astronomy is the oldest of the natural sciences, the stars and planets were often a target of worship, believed to represent their gods. While the explanations for these phenomena were often unscientific and lacking in evidence, according to Asger Aaboe, the origins of Western astronomy can be found in Mesopotamia, and all Western efforts in the exact sciences are descended from late Babylonian astronomy.
The most notable innovations were in the field of optics and vision, which came from the works of many scientists like Ibn Sahl, Al-Kindi, Ibn al-Haytham, Al-Farisi and Avicenna. The most notable work was The Book of Optics, written by Ibn Al-Haitham, in which he was not only the first to disprove the ancient Greek idea about vision, but came up with a new theory. In the book, he was the first to study the phenomenon of the pinhole camera, many European scholars and fellow polymaths, from Robert Grosseteste and Leonardo da Vinci to René Descartes, Johannes Kepler and Isaac Newton, were in his debt. Indeed, the influence of Ibn al-Haythams Optics ranks alongside that of Newtons work of the same title, the translation of The Book of Optics had a huge impact on Europe. From it, European scholars were able to build the devices as what Ibn al-Haytham did. From this, such important things as eyeglasses, magnifying glasses, Physics became a separate science when early modern Europeans used experimental and quantitative methods to discover what are now considered to be the laws of physics.
Newton developed calculus, the study of change, which provided new mathematical methods for solving physical problems. The discovery of new laws in thermodynamics and electromagnetics resulted from greater research efforts during the Industrial Revolution as energy needs increased, inaccuracies in classical mechanics for very small objects and very high velocities led to the development of modern physics in the 20th century. Modern physics began in the early 20th century with the work of Max Planck in quantum theory, both of these theories came about due to inaccuracies in classical mechanics in certain situations. Quantum mechanics would come to be pioneered by Werner Heisenberg, Erwin Schrödinger, from this early work, and work in related fields, the Standard Model of particle physics was derived. Areas of mathematics in general are important to this field, such as the study of probabilities, in many ways, physics stems from ancient Greek philosophy
The latter phenomenon is referred to as the ozone hole. In addition to these well-known stratospheric phenomena, there are springtime polar tropospheric ozone depletion events, the details of polar ozone hole formation differ from that of mid-latitude thinning but the most important process in both is catalytic destruction of ozone by atomic halogens. The main source of these atoms in the stratosphere is photodissociation of man-made halocarbon refrigerants, propellants. These compounds are transported into the stratosphere by winds after being emitted at the surface, both types of ozone depletion were observed to increase as emissions of halocarbons increased. CFCs and other substances are referred to as ozone-depleting substances. Three forms of oxygen are involved in the cycle, oxygen atoms, oxygen gas. Ozone is formed in the stratosphere when oxygen molecules photodissociate after intaking an ultraviolet photon whose wavelength is shorter than 240 nm and this converts a single O2 into two atomic oxygen radicals.
The atomic oxygen radicals combine with separate O2 molecules to create two O3 molecules and these ozone molecules absorb ultraviolet light between 310 and 200 nm, following which ozone splits into a molecule of O2 and an oxygen atom. The oxygen atom joins up with a molecule to regenerate ozone. This is a process that terminates when an oxygen atom recombines with an ozone molecule to make two O2 molecules. 2 O3 →3 O2 The overall amount of ozone in the stratosphere is determined by a balance between production and recombination. Ozone can be destroyed by a number of free radical catalysts, the dot is a common notation to indicate that all of these species have an unpaired electron and are thus extremely reactive. Cl and Br atoms destroy ozone molecules through a variety of catalytic cycles, in the simplest example of such a cycle, a chlorine atom reacts with an ozone molecule, taking an oxygen atom to form chlorine monoxide and leaving an oxygen molecule. The ClO can react with a molecule of ozone, releasing the chlorine atom.
More complicated mechanisms have been discovered that lead to destruction in the lower stratosphere as well. On a per atom basis, bromine is more efficient than chlorine at destroying ozone. As a result, both chlorine and bromine contribute significantly to overall ozone depletion, Laboratory studies have shown that fluorine and iodine atoms participate in analogous catalytic cycles. On average, a chlorine atom is able to react with 100,000 ozone molecules before it is removed from the catalytic cycle
The scientific method is a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry is commonly based on empirical or measurable evidence subject to specific principles of reasoning, experiments need to be designed to test hypotheses. The most important part of the method is the experiment. The scientific method is a process, which usually begins with observations about the natural world. Human beings are naturally inquisitive, so often come up with questions about things they see or hear. The best hypotheses lead to predictions that can be tested in various ways, in general, the strongest tests of hypotheses come from carefully controlled and replicated experiments that gather empirical data. Depending on how well the tests match the predictions, the hypothesis may require refinement. If a particular hypothesis becomes very well supported a theory may be developed. Although procedures vary from one field of inquiry to another, identifiable features are shared in common between them.
The overall process of the method involves making conjectures, deriving predictions from them as logical consequences. A hypothesis is a conjecture, based on knowledge obtained while formulating the question, the hypothesis might be very specific or it might be broad. Scientists test hypotheses by conducting experiments, the purpose of an experiment is to determine whether observations agree with or conflict with the predictions derived from a hypothesis. Experiments can take anywhere from a college lab to CERNs Large Hadron Collider. There are difficulties in a statement of method, however. Though the scientific method is presented as a fixed sequence of steps. Not all steps take place in scientific inquiry, and are not always in the same order. Some philosophers and scientists have argued there is no scientific method, such as Lee Smolin. Nola and Sankey remark that For some, the idea of a theory of scientific method is yester-years debate
Earth science or geoscience is a widely embraced term for the fields of science related to the planet Earth. Earth science can be considered to be a branch of planetary science, there are both reductionist and holistic approaches to Earth sciences. The Earth sciences can include the study of geology, the lithosphere, and the structure of the Earths interior, as well as the atmosphere, hydrosphere. Typically, Earth scientists use tools from geography, physics, biology, Geology describes the rocky parts of the Earths crust and its historic development. Major subdisciplines are mineralogy and petrology, geomorphology, stratigraphy, structural geology, engineering geology and geodesy investigate the shape of the Earth, its reaction to forces and its magnetic and gravity fields. Geophysicists explore the Earths core and mantle as well as the tectonic and seismic activity of the lithosphere, geophysics is commonly used to supplement the work of geologists in developing a comprehensive understanding of crustal geology, particularly in mineral and petroleum exploration.
Soil science covers the outermost layer of the Earths crust that is subject to soil formation processes, major subdisciplines include edaphology and pedology. Ecology covers the interactions between the biota, with their natural environment and this field of study differentiates the study of the Earth, from the study of other planets in the Solar System, the Earth being the only planet teeming with life. Hydrology is a study revolved around the movement and quality of the water and involves all the components of the cycle on the earth. Sub-disciplines of hydrology include hydrometeorology, surface hydrology, watershed science, forest hydrology. Glaciology covers the icy parts of the Earth, atmospheric sciences cover the gaseous parts of the Earth between the surface and the exosphere. Major subdisciplines include meteorology, atmospheric chemistry, and atmospheric physics, plate tectonics, mountain ranges and earthquakes are geological phenomena that can be explained in terms of physical and chemical processes in the Earths crust.
Beneath the Earths crust lies the mantle which is heated by the decay of heavy elements. The mantle is not quite solid and consists of magma which is in a state of semi-perpetual convection and this convection process causes the lithospheric plates to move, albeit slowly. The resulting process is known as plate tectonics, plate tectonics might be thought of as the process by which the Earth is resurfaced. As the result of spreading, new crust and lithosphere is created by the flow of magma from the mantle to the near surface, through fissures. Through subduction, oceanic crust and lithosphere returns to the convecting mantle, volcanoes result primarily from the melting of subducted crust material. Crust material that is forced into the asthenosphere melts, and some portion of the material becomes light enough to rise to the surface—giving birth to volcanoes
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a zone between river environments and maritime environments. They are subject both to marine influences—such as tides and the influx of saline water—and to riverine influences—such as flows of fresh water and sediment. The inflows of sea water and fresh water provide high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world. Most existing estuaries formed during the Holocene epoch with the flooding of river-eroded or glacially scoured valleys when the sea began to rise about 10. Estuaries are typically classified according to their geomorphological features or to water-circulation patterns, the banks of many estuaries are amongst the most heavily populated areas of the world, with about 60% of the worlds population living along estuaries and the coast.
The word estuary is derived from the Latin word aestuarium meaning tidal inlet of the sea, there have been many definitions proposed to describe an estuary. However, this definition excludes a number of water bodies such as coastal lagoons. This broad definition includes fjords, river mouths, an estuary is a dynamic ecosystem having a connection to the open sea through which the sea water enters with the rhythm of the tides. The sea water entering the estuary is diluted by the water flowing from rivers. The pattern of dilution varies between different estuaries and depends on the volume of water, the tidal range. Drowned river valleys are known as coastal plain estuaries. In places where the sea level is rising relative to the land, sea water progressively penetrates into river valleys and this is the most common type of estuary in temperate climates. Well-studied estuaries include the Severn Estuary in the United Kingdom and the Ems Dollard along the Dutch-German border, the width-to-depth ratio of these estuaries is typically large, appearing wedge-shaped in the inner part and broadening and deepening seaward.
Water depths rarely exceed 30 m, examples of this type of estuary in the U. S. are the Hudson River, Chesapeake Bay, and Delaware Bay along the Mid-Atlantic coast, and Galveston Bay and Tampa Bay along the Gulf Coast. They are relatively common in tropical and subtropical locations and these estuaries are semi-isolated from ocean waters by barrier beaches. Formation of barrier beaches partially encloses the estuary, with only narrow inlets allowing contact with the ocean waters, bar-built estuaries typically develop on gently sloping plains located along tectonically stable edges of continents and marginal sea coasts. They are extensive along the Atlantic and Gulf coasts of the U. S. in areas with active coastal deposition of sediments, barrier beaches form in shallow water and are generally parallel to the shoreline, resulting in long, narrow estuaries
Literacy is traditionally understood as the ability to read and use arithmetic. The concept of literacy is expanding in OECD countries to include skills to access knowledge through technology and ability to assess complex contexts. A person who travels and resides in a country but is unable to read or write in the language of the host country would be regarded by the locals as being illiterate. The key to literacy is reading development, a progression of skills that begins with the ability to understand words and decode written words. The inability to do so is called illiteracy or analphabetism, Literacy involves a continuum of learning in enabling individuals to achieve their goals, to develop their knowledge and potential, and to participate fully in their community and wider society. Literacy is thought to have first emerged with the development of numeracy, script developed independently at least four times in human history in Mesopotamia, lowland Mesoamerica, and China. The earliest forms of written communication originated in Sumer, located in southern Mesopotamia about 3500-3000 BCE, writing systems in Mesopotamia first emerged from a recording system in which people used impressed token markings to manage trade and agricultural production.
The token system served as a precursor to early cuneiform writing once people began recording information on clay tablets, proto-cuneiform texts exhibit not only numerical signs, but ideograms depicting objects being counted. Egyptian hieroglyphs emerged from 3300-3100 BCE and depicted royal iconography that emphasized power amongst other elites, the Egyptian hieroglyphic writing system was the first notation system to have phonetic values. Writing in lowland Mesoamerica was first put into practice by the Olmec and Zapotec civilizations in 900-400 BCE and these civilizations used glyphic writing and bar-and-dot numerical notation systems for purposes related to royal iconography and calendar systems. The earliest written notations in China date back to the Shang Dynasty in 1200 BCE and these systematic notations were found inscribed on bones and recorded sacrifices made, tributes received, and animals hunted, which were activities of the elite. These oracle-bone inscriptions were the ancestors of modern Chinese script and contained logosyllabic script.
According to social anthropologist Jack Goody, there are two interpretations that regard the origin of the alphabet, many classical scholars, such as historian Ignace Gelb, credit the Ancient Greeks for creating the first alphabetic system that used distinctive signs for consonants and vowels. Thus, many argue that the ancient Semitic-speaking peoples of northern Canaan invented the consonantal alphabet as early as 1500 BCE. Much of this development is credited to English archeologist Flinders Petrie. Ten years later, English Egyptologist Alan Gardiner reasoned that these contain an alphabet. In 1948, William F. Albright deciphered the text using additional evidence that had been discovered subsequent to Goodys findings and this included a series of inscriptions from Ugarit, discovered in 1929 by French archaeologist Claude F. A. Schaeffer. Some of these inscriptions were mythological texts that consisted of a 32-letter cuneiform consonantal alphabet, another significant discovery was made in 1953 when three arrowheads were uncovered, each containing identical Canaanite inscriptions from twelfth century BCE
Established scientific theories have withstood rigorous scrutiny and are a comprehensive form of scientific knowledge. It is important to note that the definition of a theory as used in the disciplines of science is significantly different from the common vernacular usage of the word theory. These different usages are comparable to the differing, and often opposing, usages of the prediction in science versus prediction in vernacular speech. The strength of a theory is related to the diversity of phenomena it can explain. In certain cases, the less-accurate unmodified scientific theory can still be treated as an if it is useful as an approximation under specific conditions. Scientific theories are testable and make falsifiable predictions and they describe the causal elements responsible for a particular natural phenomenon, and are used to explain and predict aspects of the physical universe or specific areas of inquiry. Scientists use theories as a foundation to further scientific knowledge.
As with other forms of knowledge, scientific theories are both deductive and inductive in nature and aim for predictive power and explanatory capability. Paleontologist, evolutionary biologist, and science historian Stephen Jay Gould said, “. facts and theories are different things, not rungs in a hierarchy of increasing certainty. Theories are structures of ideas that explain and interpret facts. ”The defining characteristic of all scientific knowledge, the relevance and specificity of those predictions determine how potentially useful the theory is. A would-be theory that makes no observable predictions is not a theory at all. Predictions not sufficiently specific to be tested are similarly not useful, in both cases, the term theory is not applicable. A body of descriptions of knowledge can be called a theory if it fulfills the following criteria and it is well-supported by many independent strands of evidence, rather than a single foundation. It is consistent with preexisting experimental results and at least as accurate in its predictions as are any preexisting theories and these qualities are certainly true of such established theories as special and general relativity, quantum mechanics, plate tectonics, the modern evolutionary synthesis, etc.
It is among the most parsimonious explanations, economical in the use of proposed entities or explanatory steps as per Occams razor. The United States National Academy of Sciences defines scientific theories as follows and it refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. Such fact-supported theories are not guesses but reliable accounts of the real world, the theory of biological evolution is more than just a theory. It is as factual an explanation of the universe as the theory of matter or the germ theory of disease
A concept inventory is a criterion-referenced test designed to help determine whether a student has an accurate working knowledge of a specific set of concepts. Historically, concept inventories have been in the form of tests in order to aid interpretability. Unlike a typical, teacher-authored multiple-choice test and response choices on concept inventories are the subject of extensive research, the aims of the research include ascertaining the range of what individuals think a particular question is asking and the most common responses to the questions. Concept inventories are evaluated to ensure test reliability and validity, in its final form, each question includes one correct answer and several distractors. Ideally, a score on a criterion-referenced test reflects the amount of content knowledge a student has mastered, criterion-referenced tests differ from norm-referenced tests in that the former is not used to compare an individuals score to the scores of the group. In general, item difficulty values ranging between 30% and 70% are best able to provide information about student understanding, the distractors are incorrect or irrelevant answers that are usually based on students commonly held misconceptions.
Test developers often research student misconceptions by examining students responses to open-ended essay questions, the distractors chosen by students help researchers understand student thinking and give instructors insights into students prior knowledge. Concept inventories are education-related diagnostic tests, in 1985 Halloun and Hestenes introduced a multiple-choice mechanics diagnostic test to examine students concepts about motion. It evaluates student understanding of concepts in classical mechanics. A little later, the Force Concept Inventory, another concept inventory, was developed, the FCI was designed to assess student understanding of the Newtonian concepts of force. Hestenes found that while nearly 80% of the could state Newtons Third Law at the beginning of the course. FCI data showed that less than 15% of them fully understood it at the end. These results have been replicated in a number of studies involving students at a range of institutions and that said, there remains questions as what exactly the FCI measures.
Results from Hake using the FCI have led to recognition in the science education community of the importance of students interactive engagement with the materials to be mastered. Since the development of the FCI, other instruments have been developed. These include the Force and Motion Conceptual Evaluation developed by Thornton and Sokoloff, for a discussion of how a number of concept inventories were developed see Beichner. Information about physics concept tests can be found at the NC State Physics Education Research Group website, in addition to physics, concept inventories have been developed in statistics, astronomy, basic biology, natural selection, engineering, geoscience. and computer science. In many areas, foundational scientific concepts transcend disciplinary boundaries, an example of an inventory that assesses knowledge of such concepts is an instrument developed by Odom and Barrow to evaluate understanding of diffusion and osmosis. It is therefore possible to either over-estimate or under-estimate student content mastery, the use of multiple-choice exams as concept inventories is not without controversy