A simple random sample of 50 middle-school children participated in an experimental class designed to introduce them to computer programming. At the end of the class, the students took a final exam to assess their learning. The sample mean score was 78 points, and the population standard deviation is 8 points. Compute a lower 99%

confidence bound for the mean score.

A confidence interval provides likely minimum and maximum values for a parameter.
In some cases, we are interested only in a maximum or only in a minimum. In these cases, we construct a one-sided confidence interval. A one-sided confidence interval can be an upper confidence bound, which has the form x̄ + zα σ∕√n, or a lower confidence bound, which has the form x̄ − zα σ∕√n. Note that the critical value is zα rather than zα∕2.