6.) Which of the following statements is FALSE?

a) None of these choices are false.

b) If X and Y are independent, Standard deviation of (X + Y) = Standard deviation of X + Standard deviation of Y.

c) If X and Y are independent, Variance of (X - Y) = Variance of (Y - X)

d) If X and Y are independent, Variance of (X + Y) = Variance of X + Variance of Y

e) All of these choices are false.

7.) Suppose you want to estimate the proportion of college students who go home for the summer. To use the Z distribution in your calculations, you need to check the necessary condition(s). What condition(s) do you need to check?

a) n > 30

b) np-hat and n(1-phat) at least 10

c) np and n(1-p) at least 10

d) npo and n(1-po) at least 10

8.) Which symbol do we use to find the weighted average of the squared deviations from the mean, where the weights are the probabilities?

a) sigma

b) None of the other choices is correct

c) sigma squared

d) s squared

e) s

9.) Suppose you want to investigate the average gas price in Ohio. You take a random sample of 5 gas stations in Ohio and find the sample mean is $3.75 per gallon, with a sample standard deviation of 50 cents per gallon. (Assume prices have a normal distribution.) What is your best answer?

a) None of the other choices is correct

b) $3.75 plus or minus $.50

c) $3.75 plus or minus $.62

d) $3.75 plus or minus $.44

10.) A study finds that 60% of taxpayers who owe taxes pay them during the last week of tax season. You randomly sample 100 taxpayers who owe taxes. What's the chance that at least 65 of them paid them during the last week of tax season?

a) .1539

b) .8461

c) None of the other choices is correct

d) .3461.