7.8 Heights of adults. Researchers studying anthropometry collected body girth measurements and skele- tal diameter measurements, as well as age, weight, height and gender, for 507 physically active individuals. The histogram below shows the sample distribution of heights in centimeters. 100 80- 60 40 Min Q1 Median Mean SD Q3 Max 147.2 163.8 170.3 171.1 9.4 177.8 198.1 20 0 150 160 170 180 190 200 Height (a) What is the point estimate for the average height of active individuals? What about the median? (b) What is the point estimate for the standard deviation of the heights of active individuals? What about the IQR? (c) Is a person who is im 80cm (180 cm) tall considered unusually tall? And is a person who is Im 55cm (155cm) considered unusually short? Explain your reasoning. (d) The researchers take another random sample of physically active individuals. Would you expect the mean and the standard deviation of this new sample to be the ones given above? Explain your reasoning. (e) The sample means obtained are point estimates for the mean height of all active individuals, if the sample of individuals is equivalent to a simple random sample. What measure do we use to quantify the variability of such an estimate? Compute this quantity using the data from the original sample under the condition that the data are a simple random sample. 7.28 Fuel efficiency of manual and automatic cars, Part I. Each year the US Environmental Protection Agency (EPA) releases fuel economy data on cars manufactured in that year. Below are summary statistics on fuel efficiency (in miles/gallon) from random samples of cars with manual and automatic transmissions. Do these data provide strong evidence of a difference between the average fuel efficiency of cars with manual and automatic transmissions in terms of their average city mileage? Assume that conditions for inference are satisfied. 35 25 Mean SD City MPG Automatic Manual 16.12 19.85 3.58 4.51 26 26 HI n 15 HH automatic manual City MPG