# Z-Test vs. T-Test

Need help with one psychological research question that could be answered by each of the following types of statistical tests:

a) Z test and T test for independent samples

b) T test for dependent samples

c) Rationale for both selections so I might be able to understand better

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#### Solution Preview

Both the z-test and the t-test are used to compare means (means of two samples or the mean of one sample vs. a given number). They both require independent samples taken from normally distributed populations. Here's how you choose which to use.

* You use a z-test when you know the population standard deviation, when you are looking at proportions (rather than means), or when the sample size is large (different people have different cut-off points for how large the sample needs to be -- usually around 30).

* You use a t-test when you can't use a z-test. That is, when ...

#### Solution Summary

This solution explains how to use z-tests and t-tests, and highlights when one would be used over the other. Additionally, this solution includes five reference source links for further investigation of the topic.