4. [-/0.27 Points] DETAILS BBUNDERSTAT12 7.4.014.S. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Independent random samples of professional football and basketball players gave the following information. Assume that the weight distributions are mound-shaped and symmetric. Weights (in lb) of pro football players: X, ; nj = 21 249 262 256 251 244 276 240 265 257 252 282 256 250 264 270 275 245 275 253 265 271 Weights (in lb) of pro basketball players: X2; n2 = 19 205 200 220 210 191 215 221 216 228 207 225 208 195 191 207 196 181 193 201 USE SALT (a) Use a calculator with mean and standard deviation keys to calculate X], S,, X2, and s2. (Round your answers to four decimal places.) X, = S 1 X , = (b) Let u, be the population mean for x, and let /2 be the population mean for X2. Find a 99% confidence interval for H1 - H2. (Round your answers to one decimal place.) lower limit upper limit (c) Examine the confidence interval and explain what it means in the context of this problem. Does the interval consist of numbers that are all positive? all negative? of different signs? At the 99% level of confidence, do professional football players tend to have a higher population mean weight than professional basketball players? Because the interval contains only negative numbers, we can say that professional football players have a lower mean weight than professional basketball players. Because the interval contains both positive and negative numbers, we cannot say that professional football players have a higher mean weight than professional basketball players. Because the interval contains only positive numbers, we can say that professional football players have a higher mean weight than professional basketball players. (d) Which distribution did you use? Why? The Student's t-distribution was used because of and o, are known. The standard normal distribution was used because of and oz are unknown. The Student's t-distribution was used because of and o are unknown. The standard normal distribution was used because of and o are known. Need Help? Read It