what we do when we evaluate the results of a study.  a set of procedures that are used in evaluating results. 

uses data from studies to systematically investigate research questions.

proposes that there is no effect, no difference, or no relationship among the variables being studied.

H0

there is an effect, a difference, or relationship. 

H1

occurs when we reject the null hypothesis, but the null hypothesis is true. 

type I errors are symbolized by alpha (a). 

Its like convicting an innocent person.

occurs when we fail to reject the null hypothesis, and it is, in fact, false.

type II errors are symbolized by beta (B). 

Like letting a guilty person go free.

the probability of correctly rejecting a false null hypothesis.

Power is symbolized by 1-B

The more power a study has the less likely we are to make a type II error.

the potential level of error we are willing to accept.

sets the level of significance.

the smaller the alpha level, the more rigorous our criterion for rejection of the null hypothesis.

1. random sampling - participants are selected at random from a population.

2. independence of observations - an observation is not related to any other observations within or between conditions.

3. normal distribution - permits us to use the unit normal table to determine the critical region for hypothesis test.

4. homogeniety of variance - means that the variance of the sample is the same as the variance in the population.

M-m

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sigma

cohen stated that d = .2 is a small effect size, d = .5 is a medium effect size, and d = .8 is a large effect size.