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. chi square of 0.95=10.117 chi square of 0.05=30.144

7. chi square of 0.99=9,542 chi square of 0.01=40.289

9.

  1. (7.94, 23.66)
  2. (8.59, 20.63) the width of the interval increases
  3. (6.61, 31.36) the width of the interval increases

11. (0.226, 0.542) We can be 95% confident that the popultaion S.D. pf the pH of rainwater in Tucker County, WV is between 0.226 and 0.542.

13. (734.8, 1657.5) We can be 90% confident that the popultaion S.D. of repair costs of a low-impact bumper crash on a mini or micro car is between 734.8 and 1657.5.