KEY FEATURES: Examples for each statistical expression help readers understand complex formulas A chapter on how to use the literature for power analysis walks readers through the process of making good assumptions A chapter on how to write about power analysis offers 7 key points on what needs to be included in a power analysis

# General Topics in Hypothesis Testing and Power Analysis When the Population Standard Deviation is Known: The Case of Two Group Means

### General Topics in Hypothesis Testing and Power Analysis When the Population Standard Deviation is Known: The Case of Two Group Means

This chapter is a review of population-based hypothesis testing (the $z$ test) for the difference in means between two groups. We assume we know the population variance (${\mathit{\sigma }}^{2}$) to keep things simple. In the subsequent chapters, we consider using samples (for which we have to estimate the population variance) to test differences between two groups, which affects the shape of the distributions that influence power.

### The Difference in Means as a Normally Distributed Random Variable When the Population Standard Deviation Is Known

The beauty of inferential statistics ...