Z- Test

The following videos will explain the basic statistical concepts presented on this site. The first video is a simple Z-test example with a second video on how to enter the formula in Excel.  The additional video brings the concepts together and explains the difference between the Z-test and the T-test. Please view either "definitions" slideshow with or without the narration depending on your preference. Thank you! 

Z= Mean of Sample – Mean of the Population over the standard deviation of the population/ square root of the number of observations or sample size

Why use the Z-Test?

We can draw conclusions about a population based on a sample by using a one sample z-test which compares a sample mean to the population mean. 

When to use the Z-Test?

-  Known standard deviation

-  Sample size > 30

We use normal distribution when we  know the population standard deviation and we use the Z-Score

Definitions with Narration

Definitions without Narration

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All definitions are retrieved from the following texts:

Salkind, N. J. (2016). Statistics for People Who (Think They) Hate Statistics: Thousand Oaks, CA: SAGE Publications.

Urdan, T. C. (2001). Statistics in Plain English. Mahwah, NJ: Lawrence Erlbaum Associates.

All images retrieved from creative commons - links provided on each slide

Data Set