Essentials of Mathematical Probability and Statistics

When creating confidence intervals, you started with a sample and used the sample statistic (sample mean, relative frequency, sample variance, etc.) to anchor an interval which (with high possibility) contains the corresponding population statistic $\mu ,p,{\sigma }^2\text{,}$ etc. In this section, we instead start with an educated guess for one of the population statistics $\mu ,p,{\sigma }^2$ and then statistically compare that value with the subsequently collected sample statistic.

The educated guess noted above is often called the "null hypothesis" and should be considered as a guess that one tries to disprove if possible by using a subsequent statistical sample.