Confidence Interval for a Mean using StatCrunch

If you are given summary data and asked to find a confidence interval, it is relatively easy using StatCrunch. Here is a typical problem: In this problem, you are told to use the t-distribution, but that may not always be the case. If you are given the sample standard deviation, s, instead of the population […]

Degrees of Freedom

For the present, yes, the degrees of freedom you need to find values of t are going to be equal to n-1. That’s all you need to know for the midterm. Later in the course, things will get more complicated re degrees of freedom. Let me try to give a short explanation of degrees of […]

Single-Sample, Confidence Interval for a Mean using t-distribution

Consider the following problem: The grade point averages for 12 randomly selected students are shown in the table below. Find the 99% confidence interval around the population mean, µ. Assume the population is normally distributed. Solution: This is a small sample, n < 30, and we do not know sigma. Although small samples generally are […]