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. (10.117, 30.144)

7. (9.542, 40.289)

9.

  1. (7.941, 23.66)
  2. (8.586, 20.63); the width of the interval slightly decreased
  3. (6.614, 31.36); the width of the interval increases

11. (.226, .542); we are 95% confident that these are the likely range of values

13. ($734.78, $1657.49); we are 90% confident that these are the likely range of values