Note in 31 and 33 there are some tedious calculations that I did for you. You can see the output once you knit this file.

9.2

21.

  1. type answer here. this statement is flawed because this interpretation implies that the population mean varies rather than the interval.
  2. type answer here. this statement is correct because an interval has been provided for the population mean.
  3. type answer here. this statement is flawed because this interpretation makes an implication about the individuals rather than the mean.
  4. type answer here. this statement is flawed because the interpretation should be about the mean number of hours worked by adult Amercians.

23.

type answer here. we are 90% confident that the mean drivethrough service time of Taco Bell restaurants is between 161.5 and 164.7 seconds. 25.

type answer here. increase the sample size and decrease the confidence level to narrow the confidence interval. 27.

  1. type answer here. since the distribution of blood alcohol concentrations is not normally distributed, the sample size must be large so that the distribution of the sample mean will be approximately normal.
  2. type answer here. the smaple size is less than 5% of the population.
  3. type answer here. lower bound:0.1647 upper bound:0.1693 we are 90% confident that the mean BAC in fatal crashes where the driver had a positive BAC is between 0.1647 and 0.1693.
  4. type answer here. it is possible that the mean BAC is less than 0.08g/dL. because it is possible that the true mean is not captured in the confidence interval, but it is not likely.

29.

type answer here. lower bound: 317.63 upper bound: 394.57 we are 95% confident that the mean number of licks to the center of a Tootsie pop is between 317.63 and 394.57. 31.

  1. type answer here. 4.893
  2. type answer here. lower bound: 4.690 upper bound: 5.096 we are 95% confident that the mean pH of rain water in Tucker County, West Virginia is between 4.690 and 5.096.
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. lower bound: 4.607

  2. type answer here. upper bound: 5.179 we are 99% confident that the mean pH of rain water in Tucker County, West Virginia is between 4.607 and 5.179. 33.

  3. skip

  4. 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. lower bound: 1035.8 upper bound: 2477.2 we are 95% confident the mean repair cost for a low impact collision inolving mini- and micro-vehicles is between 1035.8 and 2477.2.
  2. type answer here. the confidence interval would likely be narrower because there is less variability in the data because variability associated with the make of the vehicle has been removed.

9.3

5.

type answer here. 10.117 30.144 7.

type answer here. 9.542 40.289 9.

  1. type answer here. lower bound:7.94 upper bound:23.66
  2. type answer here. lower bound: 8.59 upper bound: 20.63 the width of the interval decreases as the sample size increases.
  3. type answer here. lower bound: 6.61 upper bound: 31.36 the width of interval increases as the confidence level increases. 11.

type answer here. lower bound: 0.226 upper bound: 0.542 we can be 95% confident that the population standard deviation of the pH of rainwater in TC, WV is between 0.226 and 0.542. 13.

type answer here. lower bound: 734.8 upper bound: 1657.5 we are 90% confident that hte population standard deviation of repair costs of a low impact bumper crash on a mini or macro-car is between 734.8 and 1657.5.