Ch 5 ppt - Lecture notes chapter five PDF

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introduction to hypothesis testing...

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Introduction to Hypothesis Testing Hypothesis Testing  A systematic procedure for deciding whether the results of a research study, which examines a sample, supports a particular theory or practical innovation that applies to the population o Example: individuals take a certain class will have a higher GPA upon graduation o Babies who take a certain formula will walk faster Core logic of hypothesis testing  Approach can seem curious or even backwards o Researcher considers the probability that the experimental procedure had no effect and that the observed results could have occurred by chance alone o If that probability the effect occurring (and it does) is sufficiently low, researcher will…  Reject the notion that experimental procedure had no effect  Affirm the hypothesis that the procedure did have an effect The null hypothesis and the research hypothesis  Null hypothesis o Opposite of desired result o Usually that manipulation had no effect  Research hypothesis o Also called the (alternative hypothesis) o Opposite of the null hypothesis o What the experimenter desired or expected all along-that the manipulation did have effect The hypothesis testing process  Step 1: restate the question as a research hypothesis and a null hypothesis about the populations  Step 2: determine characteristics of the “comparison distribution” (aka: population or sample distribution) o In this case, we are assuming we have the entire populations scores  Step 3: determine the cutoff sample score on the comparison distribution at which the null hypothesis should be rejected o The score the sample would need to have in order to decide against the null hypothesis o Also called the “critical score” o In general researchers use a cutoff with probability of 5% or less or sometimes 1% or less  Corresponds to p-values of p < .05 and p...