Chapter 4 - Introduction to Hypothesis Testing

Hypothesis Testing

A procedure for deciding whether the outcome of a study (results for a sample) supports a particular theory or practical innovation (which is thought to apply to a population).

Hypothesis

A prediction, often based on informal observation, previous research, or theory, that is tested in a research study

Theory

A set of principles that attempt to explain one or more facts, relationships, or events; psychologists often derive specific predictions from theories that are then tested in research studies.

Research Hypothesis

A statement in hypothesis testing about the predicted relation between populations (often a prediction of a difference between population means).

Null hypothesis

A statement about a relation between populations that is the opposite of the research hypothesis; statement that in the population there is no difference (or a difference opposite to that predicted) between populations; contrived statement set up to examine whether it can be rejected as part of hypothesis testing.

Comparison Distribution

The distribution used in hypothesis testing. It represents the population situation if the null hypothesis is true. It is the distribution to which you compare the score based on your sample’s results

Cutoff Sample Score

A point in hypothesis testing, on the comparison distribution at which, if reached or exceeded by the sample score, you reject the null hypothesis. Also called critical value!

Conventional Levels of Significance (p < .05, p <.01)

Levels of significance widely used in psychology.

Statistically Significant

The conclusion that the results of a study would be unlikely if in fact the sample studied represents a population that is no different from the population in general; an outcome of hypothesis testing in which the null hypothesis is rejected

Directional Hypothesis

A research hypothesis predicting a particular direction of difference between populations—for example, a prediction that the population like the sample studied has a higher mean than the population in general.

One-Tailed Test

A hypothesis-testing procedure for a directional hypothesis; situation in which the region of the comparison distribution in which the null hypothesis would be rejected is all on one side (tail) of the distribution.

Nondirectional Hypothesis

A research hypothesis that does not predict a particular direction of difference between the population like the sample studied and the population in general.

Two-Tailed Test

A hypothesis-testing procedure for a nondirectional hypothesis; the situation in which the region of the comparison distribution in which the null hypothesis would be rejected is divided between the two sides (tails) of the distribution.