# People were polled on how many books they read the previous year. how

1. Find the margin of error for the given values of c,s,and n. c=0.90,s=2.9,n=100

interval for u is: (_,_) Round to two decimal places as needed

2. Construct the confidence interval for the population mean u. c=0.98, x=8.4,s=0.3,and n=55. A 985 confidence

3. C=0.90,x=15.8,s=7.0,and n=85

A 90% confidence interval for u is (_,_)

4.Find the minimum sample size needed to estimate u for the given values of c,s,and E.

c=0.90,s=8.8,and E=1. Assume that the preliminary sample has at least 30 members.

n=

5. A random sample of 50 home theatre systems has a mean price of $120.00 and a standard deviation is $19.90. Construct a 90% and a 95% confidence interval for the population mean. Then interpret the results.

6. A random sample of 43 gas grills has a mean price of $642.40 and a standard deviation of $59.70. The 90% confidence interval is:_____ and the 95% confidence interval is:_____ Which one is wider?

7. A random sample of 34 eight ounce servings of different juice drinks has a mean of 95.8 calories and a standard deviation of 44.3 calories. The 90% confidence interval is______ and the 95% confidence interval is ______. which one is wider?

8. People were polled on how many books they read the previous year. How many subjects are needed to estimate the number of books read the previous year within one book with 90% confidence. Initial survey results indicate that o=19.3 books. A 90% confidence level requires______ subjects? Round to the nearest whole number.

9. A doctor wants to estimate the cholesterol of all 20-29 year old females. How many subjects are needed to estimate the cholesterol within 3 points with 99% confidence assuming o=13.3? Suppose the doctor would be content with 90% confidence. How does the decrease in confidence affect the sample size required?

99% confidence level requires_____ subjects

90% confidence level requires _____ subjects

How does the decrease in confidence level affect the sample size?

10. Construct the confidence interval for the population mean u using (a) a t-distribution. (b) If you had incorrectly used a normal distribution, which interval would be wider?

a._______

b._____

standard deviation was 1.31 pounds. The 90% confidence interval is (__,__).

(b) What if the sample size was 400 adults. The 90% confidence level would be (__,__)

Was normal distribution or t-distribution used? And is (a) or (b) more narrow?

11. (a) In a random sample of 10 adults the mean waste generated per person per day was 4.45 pounds and the

12. In a survey of 636 males ages 18-64, 390 say they have gone to the dentist in the past year. Construct 90% and

95% confidence intervals for the population portion. Interpret the results and compare the widths of confidence intervals.

13. In a survey of 6000 women, 3431 say they change their nail polish once a week. A 90% confidence interval for the population portion is (__,__) Round all intermediate values to the nearest thousandth.

14. A researcher wishes to estimate with 99% confidence, the proportion of adults who have high speed internet access. Her estimate must be accurate within 2% of the true portion.

What is the minimal sample size needed using a prior study that found that 54% of the respondents said they have high speed internet?

What is the minimal sample size needed assuming that no preliminary estimate is available?

15. Country A 62%.. Country B 90%… Country C 93%

2585 adults from country A, 1112 adults from country B, and 1081 adults from country C were asked if human activity contributes to global warming.

Construct a 95% confidence interval for the adults from country A.

Construct a 95% confidence interval for the adults from country B.

Construct a 95% confidence interval from the adults from country C.

16. 400 adults from the east, south, midwest, and west were asked if traffic congestion is a serious problem.

East 36%,South 32%,Midwest 25%, West 53%

95% CI for the portion of adults from the west (__,__)

95% CI for the portion of adults from the East (__,__)