9.1

25.

  1. 0.1808

  2. 2306 * .181(1-.181) = 341.84 > 10 2306 < 5% of Americans aged 18+

  3. .181 + 1.64(.008) = 0.19412 (upper) .181 - 1.64(.008) = 0.16788 (lower)

  4. We can say with 90% confidence that between .16788 and .19412 of adult Americans 18 and older have donated blood in the last 2 years.

26.

  1. 0.43

  2. 1153 * 0.43(1-0.43) = 282.6 > 10 1153 < 5% of workers and retirees in the US 25 years and older.

  3. .43 + 1.96(.0146) = .4586 (upper) .43 - 1.96(.0146) = .4014 (lower)

  4. We can say with 95% confidence that between .4014 and .4586 of workers and retirees in the US 25 years and older had less than $10,000 in savings in January 2010.

27.

  1. .5194

  2. 1003 * .5194(1-.5194) = 250.4 > 10 1003 < 5% of adult Americans

  3. .5194 + 1.96(.01578) = .55 (upper) .5194 + 1.96(.01578) = .488 (lower)

  4. It is possible, but unlikely, because we can say with 95% confidence that between 48.8% and 55% of Americans believe that TV is a luxury they could do without.

  5. .48 + 1.96(.01578) = .5109 (upper) .48 - 1.96(.01578) = .4491 (lower)

28.

  1. .75

  2. 1024 * .75(1-.75) = 192 > 10 1024 < 5% of adults 18 or older in the US.

  3. .75 + 2.58(.01353) = .7849 (upper) .75 - 2.58(.01353) = .7151 (lower)

  4. It is possible, but unlikely, because we can say with 99% confidence that between 71.51% and 78.49% of adult Americans aged 18 years or older find the issue of family values to be extremely or very important in determining their vote for president.

  5. .25 + 2.58(.01353) = .2849 (upper) .25 - 2.58(.01353) = .2151 (lower)

29.

  1. .111 + 1.96(.0205) = .1512 (upper) .111 - 1.96(.0205) = .0708 (lower)

  2. .111 + 2.58(.0205) = .1639 (upper) .111 - 2.58(.0205) = .0581 (lower)

  3. It increases as level of confidence increases.

9.2

21.

  1. Not reasonable. Confidence interval does not indicate probability.

  2. Correct.

  3. Not reasonable. Confidence interval does not describe area under a normal curve.

  4. Not reasonable. Confidence interval in this case refers to the population of adult Americans, not adults in Idaho.

23.

We can say with 90% confidence that the mean drive-through service times for fast food restauraunts are between 161.5 and 164.7 seconds.

25.

Use a larger sample size and/or a smaller confidence interval.

27.

  1. The data must be normally distributed to construct a confidence interval, which requires a larger sample size.

  2. 25000 < 5% of the population.

  3. .167 + 1.676(.0015) = .1693 (upper) .167 - 1.676(.0015) = .1647 (upper)

  4. Yes, the confidence interval could include a BAC of .08, but it wouldn’t be likely.

29.

356.1 + 1.987(19.36) = 394.568 (upper) 356.1 - 1.987(19.36) = 317.632 (lower)

31.

  2. type answer here.
data <- c(4.58,5.72,5.19,4.75,5.05,5.02,4.8,4.74,4.77,4.76,4.77,4.56)
mean(data)
## [1] 4.8925
sd(data)
## [1] 0.3194064

  1. type answer here.

  2. type answer here.

33.

  1. skip

  2. skip

data2 <- c(3148,2057,1758,663,1071,2637,3345,773,743,1370)
mean(data2)
## [1] 1756.5
sd(data2)
## [1] 1007.454

  1. type answer here.

  2. type answer here.