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. X2(0.95) = 10.117, X2 (0.05) = 30.144

7. X2 (0.99) = 9.542, X2 (0.01) = 40.289

9.

  1. lower bound = 7.94; Upper bound = 23.66

  2. Lower bound = 8.59 ; Upper Bound= 20.63. Increasing the sample size decreases the width of the interval.

  3. lower bound= 6.61; Upper bound= 31.36. Increasing the confidence interval, increases the size of the interval

11. lower bound= .226; upper bound = .542

13. lower bound = 747.8; upper bound = 1657.5