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 \(\bar{x} = 18.4\), sample standard deviation is 4.5, sample size = 35, and your confidence level is 95% this is how you can have R calculate a Confidence Interval for you.

conf_int(xbar = 18.4, size = 35, conf = .95, s = 4.5)
## [1] 16.8542 19.9458

21.

  1. (16.85, 19.95)
  2. (17.12, 19.68) It decreases
  3. (16.32, 20.48) It increases
  4. The population must be normal.

23.

  1. Incorrect, the interval varies, not the population. The population stays the same always.
  2. Correct
  3. Incorrect, we dont know anything about the individual americans, we only know the mean
  4. Inccorect, we dont know anything about the adults in Idaho, we know the mean.

25.

We are 90% sure that the drive thru time at taco bell is somewhere between 161.5 seconds and 164.7 seconds.

27.

To increase the prescision of the interval you increase the sample size and decrease the level of confidence

29.

  1. Because the histogram is highly skewed right so you need a large sample size for the data to be considered normal
  2. The sample size is less than 5% of the population
  3. (.165, .169) 90% sure that the mean number of crashes where the driver had a BAC of .165 and .169
  4. Type answer here.

31.

(1.18, 1.26) We are 99% sure that the mean number of books read in the past year was between 1.18 and 1.26.

33.

(1.08, 8.12) We are 95% sure that the mean incubation period of the SARS vius is between 1.08 and 8.12

Question

A current medicine widely available on the market is known to lower cholesterol by an average amount of 10 mg/dl. A new medicine becomes available on the market. The research publication associated with the new medicine displays a 95% Confidence Interval of the average lowering effect to be (14 mg/dl, 23 mg/dl).

  1. In deciding that the new medication is more effective then the old medication what is the Probability you made a type I error. ? Theres a 5% margin of error

  2. Describe in words what a type II error is in this situation. The medicine did not have average lowering affect between 14 and 23