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. Statement is flawed because this interpretation implies that the population mean varies rather than the interval.

  2. This statement is correct because an interval has been provided for the population mean.

  3. This statement is flawed because the interpretation makes an assumption about the individuals, not the mean.

  4. Flawed statement because the interpreatoin should be about the mean # of hours worked by adult Americans, not just adults in Idaho.

23. I am 90% confident that the mean drive through service time of TBell restaurants is between 161.5 and 164.7 seconds.

25.

Increase the sample size and decrease the Confidence Level to narrow the confidence Interval.

27.

  1. Since the distribution of BAC’s isn’t normally distributed, sample size must be large so that the distribution of the sample mean will be approx normal.

  2. Sample Size is less than 5% of population

  3. .1647 and .1693, I am 90% confident that the mean BAC in fatal crashes where the driver had a positive BAC is between those two numbers.

  4. It’s possible that the mean BAC is less than .08 because it is possible that the true mean wasn’t captured by the confidence interval, but it’s not likely.

29.

I am 95% confident that the mean number of licks to the center of a Tootsie Pop is between 317.63 and 394.57

31.

  1. 4.893

  2. I am 95% confident that the mean pH of rain water in Tucker County WV is between 4.69 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. I am 99% confident that the mean pH rainwater in Tucker County WV is between 4.607 and 5.179

  2. Margin of error increases as the confidence level increases.

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. I am 95% confident that the mean repair cost for a low impact collision involving mini and micro vehicles is between $1035.80 and $2477.20.

  2. Confidence interval would likely be narrower because there is less variability associated with the make of the vehicle has been removed.

9.3

5.

10.117 and 30.144

7.

9.542 and 40.289

9.

  1. 10.117 and 30.144, lower bound 7.94 upper bound 23.66

  2. Width of interval decreases as sample size increases 17.708 and 42.557, lower bound 8.59 upper bound 20.63

  3. Width of interval increases as the confidence level increases. 7.633 and 36.191, lower bound 6.61 upper bound 31.36.

11.

I am 95% confident that the population standard deviation of the pH of rainwater in Tucker County WV is between .226 and .542

13.

I am 90% confident that the population standard deviation of repair costs of a low impact crash between mini or micro cars is between $734.80 and $1657.50.