Download Math109 T2 SP12

North Seattle Community College
Spring 2012
ELEMENTARY STATISTICS
MATH 109 - Section 05, Test 2
STUDENT NAME: __________________________
4th June 2012
QUIZ SCORE: ______________________________
Question 1:
In a sample of 10 randomly selected women, it was found that their mean height was 63.4 inches.
From previous studies, it is assumed that the standard deviation, σ, is 2.4 inches and that the
population of height measurements is normally distributed.
a. Construct the 95% confidence interval for the population mean height of women.
b. If the sample size was doubled to 20 women, what will be the effect on the confidence
interval?
c. There is a claim that the mean height of women in the population is at least 66 inches, can
you test the claim at a level of significance of 5%?
Questions 2
If 17 out of 500 students of seniors at a school are statistics majors:
a) What is the value point estimate for the proportion of the students who are statistics majors?
b) Construct a 99% confidence interval for the proportion of all students who are statistics
majors.
c) A school known for its statistics program claims that 5% of all their seniors graduate with
statistics as a major. Can you test the claim at a level of significance of 2%?
d) If you want to estimate the proportion of all students who are statistics majors within 0.005
with 99% confidence, how many students should you survey?
Question 3:
A. Classify the two given samples as independent or dependent.
Sample 1: The weights in pounds of 26 newborn females
Sample 2: The weights in pounds of 26 newborn males
B. As part of a marketing experiment, a department store regularly mailed discount coupons to
25 of its credit card holders. Their total credit card purchases over the next three months were
compared to their prior credit card purchases during the previous three months. Determine
whether the samples are dependent or independent.
Question 4:
A statistics teacher claims that the average age for day time students is 5 years less than
that of evening students. He decides to conduct a statistical hypothesis to test this. He
selects a random sample of 35 students from each group. The data are given below. Test
the teacher’s claim at α = 0.05.
Day Students:
19
21
20
26
15
18
20
20
15
18
20
25
23
25
27
21
19
20
17
25
19
24
19
23
23
18
22
22
21
18
22
20
21
21
23
25
25
25
21
43
23
24
29
21
29
23
30
21
25
28
23
24
25
24
27
29
27
23
23
31
25
24
Evening Students
38
44
25
30
23
30
21
27
Question 5:
A nutritionist believes that obesity is more prevalent among American adults than it was in the
past. He discovers that in a study conducted in the year 1994, 380 of the 1630 randomly chosen
adults were classified as obese. However, in a more recent study, he finds 726 out of 2350
randomly chosen adults were classified as obese. At α = 0.05, do these studies provide evidence to
support the nutritionistʹs claim that the proportion of obese adults has significantly increased
since 1994?