ABSTRACT
This chapter discusses basic ideas about probability theory that are used to construct confidence intervals. It also explores a statistical technique that tells the sample size required for a stated margin of error. Like a sample mean, the best estimate of a population standard deviation is the sample standard deviation. The first technique was a confidence interval when the population standard deviation is known. It was noted that because the population standard deviation is typically not known, this type of confidence interval is not widely used. The chapter presents an outline of an algebraic variant of this first confidence-interval formula that enabled us to determine the sample size required for a given margin of error. The second, more widely used technique utilized a sample standard deviation and a newly introduced t distribution to construct confidence intervals.
