Question

What is a z-test?

Pre-test Post-test

4 1

6 9

7 2

8 3

1 6

Answer 1

A Z-test is a type of hypothesis test. Hypothesis testing is just a way for you to figure out if results from a test are valid or repeatable. For example, if someone said they had found a new drug that cures cancer, you would want to be sure it was probably true. A hypothesis test will tell you if it’s probably true, or probably not true. A Z test, is used when your data is approximately normally distributed.

When you can run a Z Test.

Several different types of tests are used in statistics (f test, chi square test, t test, etc) You would use a Z test if:

• Your sample size is greater than 30. Otherwise, use a t test.
• Data points should be independent from each other. In other words, one data point isn’t related or doesn’t affect another data point.
• Your data should be normally distributed. However, for large sample sizes (over 30) this doesn’t always matter.
• Your data should be randomly selected from a population, where each item has an equal chance of being selected.
• Sample sizes should be equal if at all possible.

How do I run a Z Test :

Running a Z test on your data requires five steps:

1. State the null hypothesis and alternate hypothesis.
2. Choose an alpha level.
3. Find the critical value of z in a z table.
4. Calculate the z test statistic (z = (x – μ) / σ),
5. Compare the test statistic to the critical z value and decide if you should support or reject the null hypothesis.

You could perform all these steps by hand.

The sample that you have given has just 5 observations. Therefore we would rather prefer t-test. Since it it is pre and post test score, use paired t test and not z test. Z test will be irrelevant here so not answering. I hope u have clearly understood what a z test is all about. All the best...!!