Example: (sample size for estimating a proportion) Suppose we wish to poll students at a large state university to determine what population of them is in favor of a new grading system. We would like a sample size that will enable us to be 90% certain of estimating the true proportion of the population of 40,000 students that is in favor of the new system within +0.02. Solution: If zo, = 0.02 and z = 1.64, then 1.640 = 0.02. p4 o, 12 Example: (sample size for estimating a proportion) Suppose we wish to poll students at a large state university to determine what population of them is in favor of a new grading system. We would like a sample size that will enable us to be 90% certain of estimating the true proportion of the population of 40,000 students that is in favor of the new system within +0.02. Solution: If zo, = 0.02 and z = 1.64, then 1.640 = 0.02. p4 o, 12