1. The length of human pregnancies from conception to birthvaries according to a distribution that is approximately Normalwith mean 266 days and standard deviation 16 days. About 68% of allpregnancies last between

a. 250 and 282days          b. 234and 298days           c.218 and 314 days      d. 250 and 266days

2. The distribution of actual weights of chocolate bars producedby a certain machine is approximately Normal with mean 8.2 ouncesand standard deviation of 0.1 ounces. What proportion of chocolatebars weigh under 8 ounces?

a. 13.5%       b.34%        c.16%       d. 2.5%

3. Sixteen weighings of a small object on a sensitive scaleresult in 5.15 grams 4 times, 5.35 grams 4 times, 5.20 grams, 4times and 5.30 grams 4 times, 16 total. If the standard deviation σof weighings on this scale is .8 grams, what is an approximate 95%confidence interval for the true weight of the object?

1. 5.25 ±.4         b.5.25 ±.2        c. 5.25±.8       d. 5.20 ±.2

4. A survey of 900 gun-owners who frequent a popular shootingrange in Texas had a nearly 100% response rate. If only 18% of therespondents thought more laws on gun control should be enacted, theconclusion that less than 20% of people in the region support moregun laws would certainly be dubious due to which of thefollowing?

a. large standard deviation of samples of size900       b. nonresponse from thesample

c. sampling bias of respondents      d. small sample size

5. Scores on a test for 8^th graders range from 0 to500. In a SRS of 400 students, the mean score is 335 and thestandard deviation is 70. The standard deviation of the samplingdistribution of xÌ…₄₀₀ is what?

1. 70/335        b.400/70       c.70/20         d.335/20

6.The weights of a sample of 400 2-year-olds in Kentucky yieldsxÌ…₄₀₀ is 21.2 pounds with a standard deviation of σ = 3pounds. What is a 95% confidence interval for the weight of alltwo-year-olds in Kentucky?
a. 18.2-21.5 pounds     b. 15.2-27.2pounds        c. 21.185-22.015pounds     d. 20.9-21.5 pounds

7.When finding confidence intervals, the interval is smallerif

    a.sample size and standard deviation arebigger    b.sample size and standard deviation aresmaller   

c.sample size is bigger, but thestandard deviation is smaller   d.sample size is smaller,but standard deviation is bigger.   

8. If the birth weights of the babies born annually in ahospital is Normal with a mean of 5 pounds 10 ounces and a standarddeviation of 5 ounces, what percentage of babies are born weighingless than 5 pounds? (No table needed.)

a. 13.5%       b.2.5%       c.16%        d. .3%

9. What percent of the babies born weigh between 5 pounds and 5pound 5 ounces? (Again no table.)

a. 13.5%       b.47.5%       c.16%        d. 34%

10. Of the 40 babies born during the first weeks of next month,how many are likely to be under five pounds?

a. 4      b.2      c. 6     d.1    

11.) A random sample of 1,600 adults in a certain country showsthat 72% have smart phones. What is a 80% confidence interval forthe percentage of adults having smart phones in this country?

1. 72%±1.85%     b.72%±1.44%    c.72%±2.24%     d.72%±1.11%

12.If 48% of the 400 voters sampled voted for candidate A overcandidate B, what is a 95% confidence for p hat, the estimate forthe percentage candidate p that A would receive?

1. 48%±2.5%      b.48%±5%     48%±10%     d.48%±1%

13.Twenty-five randomly selected students are asked how manytimes a month they eat pizza. The average for this sample isxÌ…₂₅= 11.75 times,but the population mean of all collegestudents is claimed to be μ = 10.60 times. If the null hypothesisis H₀ is μ = 10.60 times and the standard deviation σ =5 times, should the null hypothesis be rejected at the 5% level ofsignificance? (No table needed)

1. Yes       b.  No      c. Not enoughinformation      

14. Is the distribution of incomes in the US described by anormal distribution with μ equal to the mean income?

1. Yes    b. No    c. Not enoughinformation

15. The weights of baby orangutans has standard deviation 4pounds. How large a sample of baby orangutans is necessary for the95% margin of error to be .5 pounds?

a. 144      b.324      c. 256   d. 900

16. A car manufacturer says their cars average 26 miles pergallon of gas at 65 miles per hour a standard deviation of σ = 2miles per gallon.. A Consumer group tested 100 such cars and foundthe average xÌ…₁₀₀ to be 25.4 miles per gallon. Is thissufficiently small to reject the null hypothesis H₀: μ =26 miles per gallon? (No table needed.)

a. Yes     b. No     c.Not enough information.

17. What is the probability that z, the standard normaldistribution, is less than 1.75 standard deviations below the meanof zero?

a. 5%      b.4%      c.6%      d. 7.4%

18. If two random samples of the heights of adult males in NewYork are taken, one of 400, the other of 900 people, which onewould likely have the larger range from shortest to tallest?

a. the 400 person sample      b. the900 person sample    c. they’d be equal

19. The p-value of a test of the null hypothesis is 3.5%. Thismeans

a. the hypothesis is true with probability 3.5% or possibly lessthan 3.5%     b. the alternative hypothesis istrue with probability 3.5% or possibly less    c. 3.5% is the probability of finding theobserved or more extreme results when the null hypothesis (H₀) is true     d. None of theabove

20. One of the main reasons to be interested in the regressionline of y on x is that

a. one can use it to predict y-values from differentx-values     b. one can determine the standarddeviation of y    

c. one can determine from it the values of the quartiles of xand y.