You can use the following syntax to check your answers. Note the answers you get in R will not be EXACTLY the same you get by hand but they should be pretty close.

If you sample standard deviation s = 2 and the sample size = 35, and your confidence level is 95% this is how you can have R calculate a Confidence Interval for \(\sigma\).

conf_sig(s = 2, size = 35, conf = .95)
## [1] 1.617744 2.620404

9.3

5. .95= 10.177 .05=30.144

7. .99= 9.542 .01= 40.289

9.

  1. lower bound: 7.94 upper bound: 23.52
  2. lower bound: 8.59 upper bound: 20.63, the width of the interval decreases
  3. lower bound: 6.61 upper bound: 31.36, the width of the interval increases

11. lower bound: 2259, upper bound: .5419 - we are 95% confident that the population standard deviation of the pH of rainwater in Tucker is between these two numbers.

13. lower bound: 734.8 upper bound: 1657.5; we are 90% confident that the population standard deviation of repair costs of a low impact bumber crash is between these two values.