Confidence Intervals for Mean (When Sigma of Population Is Known)

Critical Z-Values In Confidence Intervals

This video introduces the concept of a critical value, and then goes through some of the most common ones that you'll see again and again in confidence interval problems: z-values for 90%, 95%, and 99% confidence intervals.

Confidence Intervals When Sigma Is Known

This video works a bunch of examples of how to plug-and-chug your way through confidence interval and margin of error problems where you are told the POPULATION standard deviation (sigma), yet somehow you can only estimate the population mean using the mean of a sample. Pretty contrived, but every prof uses these to introduce the concepts of confidence intervals.

Minimum Sample Size When Sigma Is Known

This video covers a particular type of confidence interval problem where instead of giving you a sample size and asking for the confidence interval, they give you the intended margin of error and ask you to calculate the minimum sample size to attain that level of precision. This video's formulas only work when you know POPULATION standard deviation (not just for sample).