Exam rehearsal for statistics.

1. Statistics Exam Rehearsal
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2. If using the normal approximation to a binomial distribution to calculate the
probability of getting at least 58 heads when tossing 100 coins, which area
under the normal curve must be determined?
(a) area to the right of the z-score for 57.0
(b) area to the right of the z-score for 57.5
(c) area to the right of the z-score for 58.0
(d) area to the right of the z-score for 58.5

3. The scores on an exam are normally distributed with a mean score of 70
and a standard deviation of 18. What percentage of the students
achieved 50 or more?
(a) 70 (b) 76 (c) 82 (d) 87

4. A driver’s test has 30 multiple-choice questions with 4 answer choices
for each. A person who has studied the driver’s manual has a 0.80
probability of answering any question correctly.
What is the standard deviation for driver test scores for people who have
studied?

5. The masses of 5 000 bags of potato chips are normally distributed with a
mean of 858 g and a standard deviation of 5 g. How many of the bags
will have a mass that is less than 850 g?

6. The results on an examination are normally distributed with a standard
deviation of 13.2. If the probability of having a score less than 50 is 0.04,
determine the mean for this examination.

7. The effectiveness of a new medical procedure is studied. A total of 126
randomly selected patients were surveyed, and 95 responded that they
were able to return to work within seven days of the medical procedure.
(a) Calculate a 95 percent confidence interval for the percent of the
patients returning to work within seven days.
(b) A previous survey of 94 patients who received the old medical
procedure showed that 56 patients were able to return to work within
seven days. Compare the effectiveness of the two procedures.
The new procedure is more effective for between
8% and 23% more patients 95% of the time.