Standard deviation is a measure of how far the data is spread from the mean, and can be used to assess the accuracy of the sample mean.

Type I errors are improper rejections of the null hypothesis.

Type II errors are failures to reject the null hypothesis hen it should be rejected.

Level of Significance measures the likelihood of committing a Type I error.

Power analysis measures the risk of committing a Type II error.

Regression analysis measures the relationship between two groups, and can be used to compare separate groups or the same group after an intervention. There are several ways to...

There are different tests used to perform analysis depending on the type of data available and the desired information output.
Chi squared tests are typically used to asses data that has a chi-square distribution rather than a normal distribution, though they can be used to test the variance of normally distributed data in some circumstances. Again, there are several different tyupes of chi-squared tests used for a variety of means and different forms of data.