- The Z-score allows you to decide if your sample is different from the population mean. In order to use z, you must know four things:
The population mean.
The population standard deviation.
The sample mean.
The sample size.
- Usually in stats, you don’t know anything about a population, so instead of a Z score you use a T-Test with a T Statistic.
- The major difference between using a Z score and a T statistic is that you have to estimate the population standard deviation. The T test is also used if you have a small sample size (less than 30).
