1a) Calculate the mean of the following data set:(36, 43, 37, 28, 45, 51, 30, 25, 34, 57). Express your answer to one decimal point.

Select one:

a.38.6

b.39.3

c.42.1

d.32.8

1B) Which of the following assumptions must be true in order to use the formula

to find a confidence interval estimate of the population mean?

a.

The population variance is known.

c.

The population is normally distributed.

b.

The population mean is known.

d.

The confidence level is greater than 90%.

C)The upper limit of a confidence interval at the 99% level of confidence for the population proportion if a sample of size 100 had 40 successes is:

a.

0.3040.

c.

0.4960.

b.

0.4047.

d.

0.4806.

D)Which of the following statement is true?

A. When estimating the population mean with an unknown population standard deviation, we use the student's t distribution.

B. The confidence interval for the mean will be narrower for the 95% confidence level than for the 90% level.

C. The confidence interval for the mean will be wider for the 95% confidence level than for the 90% level.

D. Holding all other factors constant, when the standard deviation increases, the interval will be narrower

E. Holding all other factors constant, decreasing the sample size will lead to a narrower interval

E) A random sample of 64 observations has a mean of 30. The populationstandard deviationis assumed to be 3. The 90%% confidence interval estimate for the population mean is:

A.

28.37 31.63.

C.

28.56 31.44.

B.

29.46 30.54.

D.

22.65 30.74.

F)A recent sample of 400 full time students showed that 114 of them worked 10 hours or more during the week.You were asked to construct a 90% confidence interval for the proportion of all full time students who work 10 hours or more a week. What sample size would you select, if your interval should have a sampling error margin of no more than 2%

A. 1378

B. 1379

C. 1957

D. 1958

E. 3378