D. P (A | B ) = P (B | A )
E. P (A and B ) = 0
Players in the National Football League weigh, on average, about 248 pounds with a standard
deviation of about 47 pounds. If four players are to be selected at random, the expected value of the
random variable W , the total combined weight of the four players, is 992 pounds. The standard
deviation of W is approximately
A. 47 pounds
B. 67 pounds
C. 94 pounds
D. 141 pounds
E. 188 pounds
- When a patient complains to the doctor about a certain set of symptoms, the doctor diagnoses the
patient with Condition A 15% of the time. If a patient with these symptoms is diagnosed with
Condition A, he or she is diagnosed with Condition B 70% of the time. A patient with these
symptoms that is not diagnosed with Condition A is diagnosed with Condition B 10% of the time.
What is the probability that a patient with this set of symptoms will be diagnosed with at least one
of these conditions?
A. 0.235
B. 0.250
C. 0.765
D. 0.850
E. 0.950 - A doctor hopes that a new surgery technique will shorten the recovery time compared to the
standard technique. To test this, he designed an experiment in which patients who required this type
of surgery were randomly assigned to the standard technique or the new technique. Then the mean
recovery time for each treatment group was compared. Assuming conditions for inference were met,
which analysis should be used?
A. A t -test for a mean.
B. A t -test for a difference in means.
C. A z- test for a mean.
D. A z -test for a difference in means.
E. A z -test for a difference in proportions. - For a class project, a student wants to see if boys and girls at their large high school differ in the
number of contacts they have stored in their phone. The student conducts a survey of 50 randomly
sampled boys and 40 randomly selected girls, and asks them to report the number of contacts.
Which of the following is true about this situation?
A. Because the population standard deviations are not known and conditions are met, the student
should use a two-sample t -test.
B. Because the sample sizes are different, the student should not use a two-sample t -test.
C. Because the sample sizes are both greater than 30, the student should not use a two-sample t -
test.
D. Because the shape of the population distribution is not known, the student should not use a two-