1. (2) A certain drug is tested for its effect on blood pressure. Seven male
patients have their systolic blood pressure measured before and after
receiving the drug. What is the outcome variable?
2. (1) The following data are the numbers of people who have called the New York State Center
for Environmental Health’s hotline for the past two weeks:
9, 15, 3, 8, 8, 11, 7, 12, 11, 15
What is the mean number of calls for the two weeks? Write your answer to the nearest tenths.
3.(1) The following data are the numbers of people who have called the New York State Center
for Environmental Health’s hotline for the past two weeks:
9, 15, 3, 8, 8, 11, 7, 12, 11, 15
What is the median number of calls?
4. Des Jarles et al. examined the failure to maintain AIDS risk reduction in a
study of intravenous drug users from NYC. The following table shows the
study subjects cross-classified according to risk reduction status (practices
risk reduction) and number of sexual partners in an average month:
Number of sexual
partners/month
None
1
>1
None
20
37
20
Risk reduction status
Not maintained
Maintained
(occasionally)
(always)
17
43
45
95
54
67
a. (2) What is the measurement scale of risk reduction status?
b. (2) What is the measurement scale of number of sexual
partners/month?
c. (2) What is the probability of a randomly selected person having
one sexual partner in an average month?
d. (2) What is the probability of a person who has one sexual partner
in an average month having a risk reduction status of none?
e. (2) What is the probability of a person whose risk reduction status is
none having one sexual partner in an average month?
5. The stress scores (on a scale 1 to 10) of students before a statistics test
are found to be approximately normally distributed with a mean of 7.08 and
a s.d. of .63. Find the probability that the stress score before a statistics test
for a randomly selected student will be:
a. (3) more than 6.25
b. (3) between 7.4 and 8.9
c. (3) between 3.4 and 6.2
6. (1)Nine men with a genetic condition that causes obesity entered a weight
reduction program. After four months the statistics of weight loss were
XBAR = 11.2, S = 9.0. Provide a 95% confidence interval for the mean of the
population of which this is a sample (assuming normality and randomness).
7. (1) In a survey study on the incidence of depression in a population of psychiatric
hospital administrators, scores on a depression measure were obtained from 86
respondents. The observed mean score was 62, with a standard deviation of 16.
What kind of table would you use in constructing a 99% confidence interval for
the mean depression score?
8. (1) State True or False. As the sample size (n) increases, the mean of a random sample is less
likely to be near the mean of the population.
9. (1) Which of the following is a true statement regarding the comparison of t-distributions to
the standard normal distribution?
a. The normal distribution is symmetrical whereas the t-distributions are slightly skewed.
b. The proportion of area beyond a specific value of t is less than the proportion of area beyond
the corresponding value of z.
c. The greater the df, the more the t-distributions resemble the standard normal distribution.
d. All of the above.
e. None of the above
10. (2) A sample of size 26 is taken from a normal population. Then a 95%
confidence interval is set up with XBAR = 30 and s = 20. The value
you would find in the table to complete the information necessary to
obtain the interval would be:
Select one:
a. 1.711
b. 1.708
c. 2.060
d. 2.064
e. 1.960
11. (3 ) A researcher claims that less than 15% of adults in the general US population are allergic
to a medication. The results from his study showed that in a random sample of 100 adults only
10 said that they had such an allergy.
Test if the researcher’s claim is justified (use a one-sided test because you are given the
anticipated direction of the difference).
– What test will you use?
– State H0 and H1 for this test.
– Provide the p-value and make a final conclusion about the data using the significance level of
0.05.
(Hint: this question is about comparing a proportion to some given value)
12. (4) The Consumer Reports magazine tested two types of winter tires, SnowFlake and
SnowMan, to determine how well each brand performs on ice when stopping from 15 mph. 12
sets of the SnowFlake tires and 12 sets of the SnowMan tires were tested. The results showed
that for the SnowFlake tires the sample mean stopping distance was 55 feet with the sample
standard deviation of 7 feet, while for the SnowMan tires the sample mean stopping distance was
57 feet with the sample standard deviation of 4 feet. Assume that the data are normally
distributed.
Can you conclude that there is a significant difference in the stopping distance between these two
types of tires?
– What test(s) will you use?
– State H0 and H1 for these tests.
– Provide the p-value and make a final conclusion about the data using the significance level of
0.05.
