Bias, Correlation, Causation, Hypothesis, Law, & Theory

Main Topics Take at least one note for each of these topics: Bias Correlation Causation Hypothesis Law Theory Remember, you decide what is important to write down.

Be Objective Bias-when what the scientist expects changes how the results are viewed May cause a scientist to prefer results of one trial over another. If the advantages of a product being tested are used in a promotion and the drawbacks are not presented

How to Reduce Bias Run as many trials as possible. Keep accurate notes of each observation made. Use data that is measurable. The experiment must be repeatable. Findings are supportable when other scientists perform the same experiment and get the same results.

Definition of Causation When a specific action causes a second event to happen Cause and effect

Definition of Correlation when two or more things or events tend to occur at the same time and might be associated with each other, but aren’t necessarily connected by a cause/effect relationship

Researchers don’t jump to conclusions.

Well, sometimes we do…but we try not to. Example: Ulcers.

Causation? We used to believe that ulcers were caused by stress and spicy food.

Causation There was a correlation between the independent variables (stress/spicy food), and the dependent variable (ulcers) but the independent variables were NOT the cause. We now know that ulcers are caused by a corkscrew-shaped bacterium Helicobacter pylori (H. pylori).

Correlation Natural stomach acids and spicy food may have irritated the already damaged stomach and small intestine, but they never caused the ulcers. For more information on ulcers, see http://www.cnn.com/HEALTH/library/DS/00242.html

Causation Correlation studies help us determine the existence of a relationship between variables. This relationship can help us design more precise, experimental studies to better understand our environment and causation.

Hypothesis, Laws, Theories Thanks to T Landry

Hypothesis: This is a specific prediction based upon observation. It is a rational explanation of a single event or phenomenon based upon what is observed, but which has not been proved. Most hypotheses can be supported or refuted by experimentation or continued observation.

Scientific Law This is a statement of fact meant to describe an action or set of actions. It is generally accepted to be true and universal Sometimes can be stated as a single mathematical equation. Scientific laws must be simple, true, universal, and absolute.

Examples of Laws Law of gravity Newton's laws of motion the law of conservation of mass and energy, Hook’s law of elasticity.

Examples of Laws Law of gravity Newton's laws of motion the law of conservation of mass and energy, Hook’s law of elasticity. Hooke's law accurately models the physical properties of common mechanical springs for small changes in length

Laws Come With Specific Conditions Newton's law of universal gravitation only applies in weak gravitational fields

Theories Theories are constructed to explain, predict, and master phenomena.

Theories in Science A scientific theory must: be testable or lead to predictions that are testable involve reproducible results

Laws vs theories A law describes a single action, whereas a theory explains an entire group of related phenomena. A law differs from a scientific theory in that it does not explain; it is the results of repeated observation.

Right or Wrong? Theories are abstract and conceptual, and to this end they are never considered finally proven. Instead, they are supported or challenged by observations in the world.

Falsified, Revised, Shelved Sometimes theories are falsified and discarded, because new observations don’t match the theory. More often, theories are revised or tweak to include and conform to new observations.

Examples of Scientific Theories Astronomy: Big Bang Theory Biology: Cell theory — Evolution — Germ theory Chemistry: Atomic theory — Kinetic theory of gases Climatology: Theory of Global Climate Change (due to human activity) Geology: Plate tectonics Physics: Theory of relativity

Biology Miasma theory of disease A representation of the cholera epidemic of the nineteenth century depicts the spread of the disease in the form of poisonous air. Replaced by the Germ Theory of Disease

Geology Continental drift was superseded by plate tectonics Plate tectonics, a modern update of the old ideas of Wegener about "plowing" continents, accommodates continental motion through the mechanism of seafloor spreading.

Progression of atomic theory A schematic representation of the Plum pudding model of the atom.

Progression of atomic theory Rutherford Model

Progression of atomic theory Rutherford Bohr Model

Progression of atomic theory