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; 30.114

7. 9.542; 40.289

9.

  1. 7.94; 23.66
  2. 8.59; 20.63 - interval width decreases as sample size increases
  3. 6.61; 31.36 - interval width increases as confidence level increases

11. we are 95% confident that that the population standard deviation of the rainwater is between .226 and .542

13. we are 90% confident that the population standard deviation of the repair is between $734.80 and $1657.50