- (B) The steeper part of the graph corresponds to the higher bars on a histogram. So the higher bars
would be on the left with a tail stretching toward the right.
- (E) No causal relationship is established simply because of a correlation. But r 2 is 0.09.
- (C) Nonresponse bias is a problem because the kind of people who don’t respond might feel
differently from those who do. Getting responses from more of the people that do respond won’t fix
the problem.
- (B) Under the null hypothesis, the proportions are the same, so the standard error formula is based on
the pooled proportion .
- (E) Choice E implies a causal relationship, which is not justified because this is an observational
study.
- (E) The margin of error is largest for = 0.5, so if ≠ 0.5, the margin of error will be even smaller.
So use . Solve for n and round up.
- (A) They have all the data for November, so there is no inference to do. 50% of the donations are
above the median, not the mean. A is the only conclusion we can make.
- (A) n is not large enough to use a normal approximation. This is a binomial situation, and choice A
correctly applies the binomial calculation.
- (E) Using s in the denominator makes Max’s an approximate t -distribution. That has heavier tails and
more spread than Claire’s approximately normal distribution.
- (C) Multiplying affects both measures of location and spread. Adding affects only measures of
location.
- (C) This is easiest to see in a two-way table.
The required probability is 0.096/0.114 = 0.842.
- (D) The confidence interval is based on one sample of many possible samples. The process has a
95% chance of capturing the true proportion of all Americans within the interval created. But there is
nothing special about that one interval.
- (A) That is the multiplication rule for independent events.
- (C) Since these are four independent occurrences of W , the variances add. So the standard deviation
is
- (A) The bottom path in the tree diagram shows that the probability that a patient has neither condition
is 0.85 0.90 = 0.765. 1 – 0.765 = 0.235.
