Before answering comment what is being tested
CHAPTER 7 SAMPLING DISTRIBUTIONS 528 (e) the person measuring the children's weights does so 7.8 Which of the following statements about the sampling without any error. distribution of the sample mean is incorrect? T7.10 Suppose that you are a student aide in the library (a) The standard deviation of the sampling distribution and agree to be paid according to the "random pay will decrease as the sample size increases. system. Each week, the librarian flips a co a coin. If the (b) The standard deviation of the sampling distribution mes up heads, your pay for the week is $80 measures how far the sample mean typically varies If it comes up tails, your pay for the week is $40 from the population mean. You work for the library for 100 weeks. Suppose we (c) The sample mean is an unbiased estimator of the choose an SRS of 2 weeks and and calculate your aver . population mean. age earnings x. The shape of the sampling distribu- tion of x will be (d) The sampling distribution shows how the sample mean is distributed around the population mean. (a) Normal. (e) The sampling distribution shows how the sample is (b) approximately Normal. distributed around the sample mean. (c) right-skewed. 17.9 A newborn baby has extremely low birth weight (d) left-skewed. ELBW) if it weighs less than 1000 grams. A study of the health of such children in later years examined a (e) symmetric but not Normal. random sample of 219 children. Their mean weight at birth was x = 810 grams. This sample mean is an T7.11 An SRS of size 100 is taken from Population A unbiased estimator of the mean weight u in the popu- with proportion 0.8 of successes. An indepen dent SRS of size 400 is lation of all ELBW babies, which means that 400 is taken from Population B (a) in all possible samples of size 219 from this population, with proportion 0.5 of successes. The sampling the mean of the values of x will equal 810. distribution of the difference (A - B) in sam- (b) in all possible samples of size 219 from this population, deviation? ple proportions has what mean and standard the mean of the values of x will equal u. (a) mean = 0.3; standard deviation = 1.3 (c) as we take larger and larger samples from this population, x will get closer and closer to u. (b) mean = 0.3; standard deviation = 0.40 (d) in all possible samples of size 219 from this population, (c) mean = 0.3; standard deviation = 0.047 the values of x will have a distribution that is close to (d) mean = 0.3; standard deviation = 0.0022 Normal. (e) mean = 0.3; standard deviation = 0.0002
