a) The standard error is 1/12 hours or 5 minutes
b) a 95% CI id 12 hrs 50 min to 13 hrs 10 min
c) The SEM is 0.062, so the measure of variability is 0.104. A 95% CIfor the difference is 1.79 to 2.21 hours.
Problem 4.
5%
Problem 5.
No. THey have the necessary information on the etire population, so that they can compute it directly.
Problem 7.
a) with 95% confidence,we could concluded that the risk of disease was greater uderone of the conditions.
b) We could not conclude that the risks under the two conditions were different (but we could not go as far as saying that tey are equal)
Problem 10.
This would have been misleading because the ineval does not lie eniely above zero, so there is a good chance thatthe difference in the sampe means does not represent a real difference in the populations.
Problem 11.
a) the CI is 63.83 to 65.45
b) the CI is 61.97 to 65.97
c) the interva in part b is wider because the sample size is smaller. We could not conclude that there is a diference in the mean ages because there is overlap in the two intervals.
d) the interval is -1.49 to 2.83. This interval does not lieentirely aove zero, so there is some chance that the difference in these sample means does not represent a real difference in the population of strong left-handers and right handers.
Problem 13.
The study says that with 95% certainty, we know that people breathingsecondhand smoke are between 8% and 150% more likely to get lung cancer than those who do not breath it.
Problem 14.
This study exhibited a large placebo effect, meaning that scores changed even for those women taking a placebo instead of calcium. A comparison of the calcium group third cycle scores to their own baseline would include both the placebo effect and the actual impact of taking calcium. Thus it would overstate the influence of taking calcium.
Problem 16.
The CI is 12% to 22%. This interval lies entirely above 0, so it does indicate that the opinion on this issue among American adults had changed.
Problem 17.
Method 1. the differences within couples is desired not across sexes. We can be 95% certain that on average British husbands are between 1.6 and 2.9 years older than their wives.
Problem 18.
Method 2 would be appropriate because we are not interested in the differences within couples, but rather between the mean for men and the mean for women. The CI is 4.58 to 5.62 inches. We canbe 95% certain that the average height for British men is between 4.58 and 5.62 inches taller than the average height for British women.
Problem 19.
a) Neither the woen aking the pills of the medical personnel with whom they interacted knew who had which type of pill.
b) Because this was a randomized experiment and not an observational study, it is actually possibleto make a causal conclusion. Confounding variables if present should be equally presentin both groups, so the differences seen between the calcium and placebo-treated groups can be attributed to the calcium.