North Seattle Community College
Winter Quarter 2012
Elementary Statistics-Math109
Test 4 – 6.4, 7.1, 7.2, 7.4, 7.5, 8.1, 8.4, 9.1, 9.2
Name:_________________________________
Score:_________________________________
1. A random sample of the weights ( in ounces) of 17 superzoom digital cameras is shown
in the stem- and- leaf plot. Use a 95% level of confidence for the confidence interval of
the variance
Key 1 | 3 = 13
0 7889
1 0134555779
2 14
3
5
2. A travel agency estimates that the standard deviation of the room rates of hotels in a
certain city is no more than $ 30. You work for a consumer advocacy group and are
asked to test this claim. You find that a random sample of 21 hotels has a standard
deviation of $ 35.25. At α = 0.01 do you have enough evidence to reject the agency’s
claim?
3. A polling agency reports that over 16% of U. S. adults are without health care coverage.
In a random survey of 1420 U. S. adults, 256 said they did not have health care coverage.
At α = 0.02 is there enough evidence to support the agency’s claim?
4. In a survey of 1000 U. S. adults in 2007, 57% said it is likely that life exists on other
planets. In a recent year, in a survey of 1000 U. S. adults, 53% said it is likely that life
exists on other planets. At α = 0.01, can you support the claim that the proportion of
U.S. adults who believe it is likely that life exists on other planets is less now than in
2007?
5. The U. S. Department of Agriculture claims that the mean cost of raising a child
from birth to age 2 by husband- wife families in rural areas is $ 10,380. A random
sample of 800 children ( age 2) has a mean cost of $ 10,240 with a standard
deviation of $ 1561. At α = 0.01 is there enough evidence to reject the claim?
6. In a fast food study, a researcher finds that the mean sodium content of 42
Wendy’s fish sandwiches is 1010 milligrams with a standard deviation of 75
milligrams. The mean sodium content of 39 Long John Silver’s fish sandwiches is
1180 milligrams with a standard deviation of 90 milligrams. At α = 0.01 is there
enough evidence for the researcher to conclude that the Wendy’s fish sandwich
has less sodium than the Long John Silver’s fish sandwich?
7. The ages ( in years) and the number of hours of sleep in one night for seven
adults.
a. Calculate the correlation coefficient r. Interpret the relationship.
b. Plot the points on a graph.
c. Draw a line by hand that you think adequately represents this data and
determine the equation of the line. (your guestimate)
d. Now use the formulae prescribed in the text book to determine the equation of
the line. (theoretical best estimate)
e. Interpret the relationship between the y and x in words.