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. {7.94, 23.66}
  2. {8.59, 20.63} As the sample size increases, the width of the confidence interval decreases.
  3. {6.61, 31.36} As the confidence level increases, the width of the interval increases.

11. {.226, .542} We are 95% confident that the population standard deviation of the pH rainwater in Tucker county is between .226 and .542.

13. {$734.8, $1657.5} We are 90% confident that the population standard deviation of repair costs of a low impact bumper cras is between $734.8 and $1657.5.