ASSIGNMENT
DUE
November 2, 2006
1) A 1990 Roper Organization poll of 3000 randomly selected women found that 58% of the respondents
endorsed the statement “Most men think only their own opinions about the world are important.” The
margin of error was  2% . (source: “Comments concerning increased female negativism towards males,”
Contemporary Social Psychology, vol 15 (1991), no.2, p 53.)
A) What is the margin of error?
B) What can you say about the other 42% of the respondents?
C) How would you use the margin of error to interpret this result?
2) In a sample of 28 swordfish has a mean mercury concentration level of 1.09 ppm with a 95% confidence
interval for the population level from .90 ppm to 1.28 ppm. (source: “Mean and variance of partially
truncated distributions,” Biometrics, vol. 36 (1980), pp. 531-536.)
A) What is the margin of error?
B) How do you interpret this confidence interval?
C) Does it seem as if the mercury concentration level satisifies the legal limit of
no more that 1.00 ppm?
3) In a sample of college male seniors, the mean height is 71 inches with a standard deviation of 2.1
inches. A 95% confidence interval for the corresponding mean height in the population from which the
data came goes from 70.4 to 71.6 inches. Note that the mean height of American males is 69.1 inches.
(source: The New York Times, July 26, 1992, P. E5.)
A) What is the margin of error?
B) How do you interpret this confidence interval?
C) Compare this confidence interval to the mean of American males. What does this tell you
about the heights of college seniors compared with the heights of all Americans?
4) In a sample of 49 employees of a large business, the mean number of days (in a year) lost to illness by
employees was 7.0 with a standard deviation of 2.5 days.
A) Find a 95% confidence interval for the mean number of days lost to illness for the entire
company. How do you interpret this interval?
For Next time:
Reread pages 320-329
Read pages 329-333
Hand in the following
1) Exercises in Chapter 13
Apply your Knowledge: 7,9,12
Exercise on page 333: 16b,18a,20,24