Confidence intervals

- Let's say you're interested in determining the mean height…of the employees in your company,…but there are 500 employees.…It's not practical to measure every one of them.…So, you take a sample of 20 employees…and find that the sample mean is 69.87 inches.…How confident are you in saying that the population mean…is exactly 69.87 inches?…You probably have a zero percent confidence level.…Now, how confident will you be in saying…that an interval of zero to 100 inches…includes the population mean?…Now you're probably 100% confident.…

But having a 100% confidence level…with such a wide interval is not useful.…That interval is called the confidence interval,…which is a statistically calculated range of values…that contains a population parameter, such as the mean,…with a certain level of confidence.…It's most commonly set at 95%.…Here is a graphical summary of the sample data…for mean height using Minitab.…You can see the sample size is 20…along with all the summary statistics.…

The sample mean is 69.871.…The 95% confidence interval for the mean is 69.036…