INDUCTIVE VS DEDUCTIVE REASONING Which type of reasoning
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INDUCTIVE VS. DEDUCTIVE REASONING • Which type of reasoning was our experiment yesterday an example of?
INDUCTIVE REASONING: STARTS WITH DATA • We collected data (period as a function of mass) • We analyzed data to find a pattern. (mass does not affect period) • That pattern leads us to the conclusion: Whatever determines the period, mass is NOT a part of it. • So what does affect period? Inductive reasoning uses data to form a hypothesis or theory.
DEDUCTIVE REASONING: STARTS WITH THEORY 1. According to this formula, what happens to the period (T) as length (L) increases? T = period p = 3. 14 L = length g = 9. 8 m/s 2 (acceleration due to Earth’s gravity) 2. According to this formula, does mass affect period? 3. Calculate the expected period for a length of 0. 50 m (approximately the length of your pendulum).
DEDUCTIVE: CONFIRM THEORY • If this theory of pendulum motion is true: • Predicted T for L = 0. 50 m = 1. 4 s • Predicted T for L = 0. 20 m? ? ? Deductive reasoning uses a hypothesis or theory to make predictions about data.
SCIENCE HAS A SPECIAL CLAIM TO TRUTH • Because of the requirement for repeatability and objective measurement, science has a unique ability to describe reality with certainty. • I will make a scientific claim: • “The mass of a pendulum bob has no effect of its period. ”
EVIDENCE = DATA • In science two types of evidence are permitted to support a claim: • Measurements collected during an experiment. • Previously established scientific principles, (which are also based on measurements) Table 1. Pendulum periods
REASONING: ANALYSIS OF THE DATA • Only Mathematical and logical reasoning are permitted. • Figure 1, above, shows a line of best fit for the averages of periods observed for each mass. The slope of the line is negligible (+/- 0. 1 m. S), therefore there is no correlation between mass and pendulum period.
RECAP: GOOD SCIENCE • Makes a CLAIM about the relationship between 2 or more variables. • Provides EVIDENCE in the form of data and/or accepted scientific principles. • Uses mathematical and/or logical REASONING to interpret the evidence. And that’s where new knowledge comes from.
