STA 2023 Lecture Notes - Lecture 28: Variance, Sample Size Determination, Confidence Interval
Document Summary
Allows you to choose a random sample of size n that produces results that are within an acceptable distance from the population value. As long as the sampling is executed properly, excellent estimates result from relatively small samples, no matter how large the population size. Se = precision/sampling error (have control) z = discussed in sections 7. 3 and 7. 4. = sample variance (no control); known population standard deviation or a best guess for it. An estimate is needed of the average age of customers in a department store correct to within 2 years with probability . 98. Confidence level: 0. 98 n = (2. 332)(7. 52)/22 = 76. 39 n = 77. To decrease the needed sample size n, you can: Increase the sampling error (on denominator: decrease the confidence (on numerator, you have no control over standard deviation. The airport transit association is considering a poll to determine the percentage of adults who have never flown in an airplane.
