POLS 581 Homework 5
Fall 2008
This homework may be done by hand or turned in as a PDF. Show your work for all calculations.
1. Calculate the expected frequencies for the following crosstab:
White Respondents Black Respondents Total
Did Not Vote in 2004 188
Did Vote in 2004 750
Total 781 157 938
2. Given the following crosstab of diamonds by color, (a) interpret the 2 statistic. (b) What would be
P( and Red) if the two events were independent?
| Red
Diamond | No Yes | Total
-----------+----------------------+----------
No | 26 13 | 39
Yes | 0 13 | 13
-----------+----------------------+----------
Total | 26 26 | 52
Pearson chi2(1) = 17.3333
3. Assume that 12% of the American population is Black, 5% holds a PhD, and that the proportion of
Blacks who hold a PhD is 1 in 1000. (a) What proportion of the American population is Black and holds
a PhD? (b)
4. For the following table by factors, find the following probabilities:
(a) P(gun owner)
(b) P(union household)
(c) P(gun owner | union household)
(d) P(gun owner union household)
(e) If the two events were independent, what would be P(gun owner union household)?
(f) Are the two events independent according to probability theory?
(g) What does a chi-square test tell us about these two events?
Does R have a |
gun in his or | Anyone in HH belong
her home or | to labor union?
garage? | 0 No 1 Yes | Total
--------------+----------------------+----------
1 Yes | 337 86 | 423
5 No | 640 116 | 756
--------------+----------------------+----------
Total | 977 202 | 1,179
