QUESTION 1

Agroup of researchersintends to estimate the average time to perform a medical procedure. From the data sampled previously, they believe that the average time is 42 minutes with a standard deviation of 12 minutes. They want the 95% confidence interval to have a margin of error of no more than 2 plus or minus minutes. How large a sample do they need?

A.333

B.71

C.34

D.139

4 points

QUESTION 2

A inspector wishes to estimate the percentage of the food items in a store that have passed the expiration date. It isbelieved that the percentage of items passed the expiration date in this storeisaround 5%. How large a sample does the inspector need in order to have a 95% confidence that the margin of error is within plus or minus 2%?

A.25

B.1883

C.457

D.2401

4 points

QUESTION 3

The Central Limit Theorem is important is statistics and it says,

A.For any population, it says the sampling distribution of the sample mean is approximately normal, regardless of sample size.

B.If one takes a relative large random sample from a population, it says the population would be approximately normally distributed.

C.For a sample of any size taken from any population, the sampling distribution of the sample mean would be approximately normal.

D.If one takes a relative large random sample from a population, the sampling distribution of the sample mean would be approximately normal, regardless of the distribution of the population.

4 points

QUESTION 4

The birth weights (in lb) for a random sample of 5 infants from a particular population were recorded as the following: 5.9, 6.2, 6.9, 7.0, 7.2. The birth weights of this population follow a normal distribution. Which of the followings is the correct 90% confidence interval estimate for mean weights of this population? (If not exact, choose the closest one. Carry to at least the second decimal place in each calculation.)

A.We can be 90% confident that the average infant birth weight is between 6.15 lb and 7.12 lb.

B.We can be 90% confident that the average infant birth weight is between 6.27 lb and 7.36 lb.

C.We can be 90% confident that the average infant birth weight is between 6.11 lb and 7.17 lb.

D.We can be 90% confident that the average infant birth weight is between 6.22 lb and 7.05 lb.

E.We can be 90% confident that the average infant birth weight is between 5.95 lb and 7.33 lb.

4 points

QUESTION 5

In a study, researchers wish to find out what percent of the people in a population that has high systolic blood pressure (greater than or equal to 140 mm Hg.). From a randomly selected sample of 1000 individuals from this population, 65 of them have high systolic blood pressure. Which of the followings is the 90% confidence interval estimate for the percentage of people that has high systolic blood pressure in this population.

A.(5.0%, 8.0%)

B.(4.8%, 8.2%)

C.(4.6%, 8.4%)

D.(5.2%, 7.8%)

4 points

QUESTION 6

In a study, the percentage of people that have watched movie in a public theater in a community during the past six months was estimated and it was 14%. The report also stated a 95% percentage confidence interval estimate, and it was (12%, 16%). Which of the following statements is correct if the confidence interval was computed using Wald's normal approximation method?

A.The margin of error is not stated explicitly in the report, and we have no way to know it.

B.The margin of error in this study is 4%.

C.There is no chance that the population percentage is less than 10%.

D.The margin of error in this study is 2%.