A physical therapist wants to determine the difference in the proportion of men and women who participate in regular sustained physical activity. What sample size should be obtained if he wishes the estimate to be within four percentage points with 95​% ​confidence, assuming that ​(a) he uses the estimates of 21.1​% male and 19.6​% female from a previous​ year? ​(b) he does not use any prior​ estimates? ​(a) n=   ​(Round up to the nearest whole​ number.) ​(b) n=   ​(Round up to the nearest whole​ number.)

It is calculated that, in order to estimate the true mean amount of money spent on textbooks this semester by U of M students to within $40 with 99% confidence, we need a sample of 100 students. What sample size would be required to estimate the true mean amount of money spent on textbooks to within $10 with 99% confidence?

A researcher wishes to estimate the proportion of adults who have​ high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.03 with 99​% confidence if​(a) she uses a previous estimate of 0.48​? ​(b) she does not use any prior​ estimates?   ​n= ​(Round up to the nearest​ integer.)

1.  An experimenter feels that a population standard deviation is no larger than 17.0and would like to construct a 95% two-sided t-interval for the population mean that has alength at most 2.8. What sample size would you recommend?

For each of the following settings in Exercises 2.1.1-2.1.4, (i) identify the variable(s) in the study, (ii) for each vari- able tell the type of variable (e.g., categorical and ordinal, discrete, etc.), (iii) identify the observational unit (the thing sampled), and (iv) determine the sample size. A total of 129 persons donated blood. For each of them, the blood type and cholesterol levels were recorded. 2.1.3 (a) A biologist measured the number of leaves on each of 25 plants. 2.1.1 (a) A paleontologist measured the width (in mm) of the last upper molar in 36 specimens of the extinct mam- mal Acropithecus rigidus. (b) The birthweight, date of birth, and the mother's race were recorded for each of 65 babies (b) A physician recorded the number of seizures that cach of 20 patients with severe epilepsy had during an eight-week period. 2.1.4 (a) A conservationist recorded the weather (clear, partly cloudy, cloudy, rainy) and number of cars parked at noon at a trailhead on each of 18 days.…

A researcher wishes to estimate the proportion of adults who have​ high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.01 with 90​% confidence if ​(a) she uses a previous estimate of 0.38​? (b) she does not use any prior​ estimates?

A researcher wishes to estimate the proportion of adults who have​ high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.03 with 90​% confidence if ​(a) she uses a previous estimate of 0.34​? ​(b) she does not use any prior​ estimates?