28. The standard deviation of a variable is 15. If a sample of 100 individuals is selected, what size is necessary to double the standard error of the mean? 200 25 400 50

8. Suppose that the distance of fly balls hit to the outfield (in baseball) is normally distributed with a mean of 210 feet and a standard deviation of 50 feet. Let X = distance in feet for a fly ball. Find the 80th percentile of the distribution of fly balls. (Round your answer to one decimal place.) _____ ft

86. What is the standard deviation of the following set of sample data?   18    7    9    7    18    17 2.1 2.3 5.5 5.1

9. Write the appropriate notation symbol that corresponds to the given parameter or statistic. a. Population Mean: tof births d. Population Standard Deviation: variable? Triplets b. Sample Mean: e. Sample Variance: c. Population Variance: f. Sample Standard Deviation: sihle for the standard deviation of a list of numbers to equal zero?