You plan to construct a 99% confidence interval for the mean & of a Normal population with (known) standard deviation o. By using a sample size of 400 rather than 100, you can reduce the margin of error by a factor of Select one: a. 2 (the new margin of error will be half that of the one based on 100 observations). O b. 4 (the new margin of erfor will be 1/4 that of the one based on 100 observations). O c. 16 (the new margin of error will be 1/16 that of the one based on 100 observations). O d. none of the above-it depends on the value of o. Clear my choice The amount of time customers at a "Quick-Change" motor oil store spend waiting for their cars to be serviced has the Normal distribution with mean and standard deviation o= 4 minutes. It is company policy that the customer wait time should be 20 minutes (or less). The manager of a particular store selects a random sample of 150 customer wait times and observes a mean wait time of 21 minutes. Reference: Ref 14-1 If the manager had selected more customers for her sample, the margin of error in a 95% confidence interval using this data would Select one: a. become larger or smaller, depending on the sample taken. O b. become smaller. O c. not change. O d. become larger. A researcher selects a random sample. A 90% confidence interval for a population mean Select one: O a. is an interval with margin of error + 90%. stion b. has the property that if we repeatedly selected our random sample in exactly the same way, each time constructing a different 90% confidence interval for , then in the long run 90% of those intervals would contain . O c. (a) and (b) are both true. O d. is an interval that has width . 90. Clear my choice A random sample of eighty-five students in Chicago city high schools takes a course designed to improve SAT scores. Based on these students, a 90% confidence interval for the mean improvement in SAT scores from this course for all Chicago city high school students is computed as (72.3, 91.4) points. The correct interpretation of this interval is: Select one: ior a. that 90% of the students in the sample had their scores improve by between 72.3 and 91.4 points. O b. that 90% of the students in the population should have their scores improve by between 72.3 and 91.4 points. O c. if you use a 90% confidence interval often, in the long run, 90% of your intervals will contain the true parameter value (in this case () O d. None of the above. Clear my choice