AMS 5 Practice 6
Chapter 8, #1, 2, 4, 5, 7, 10, 11
1. A study of the IQs of husbands and wives obtained the following results:
for husbands, average IQ = 100, SD = 15
for wives, average IQ = 100, SD = 15
r = .6
One of the following is a scatter diagram for the data. Which one? Say briefly why you
reject the others.
1) D, because (100, 100) is roughly in the middle of the oval and the oval contains points
outside of 1 SD.
2. (a) For a representative sample of cars, would the correlation between the age of the car
and its gasoline economy (miles per gallon) be positive or negative?
(b) The correlation between gasoline economy and income of owner turns out to be
positive. How do you account for this positive association?
2a) Negative, since unlike wine, mechanical parts don’t get better with age.
2b) More affluent people can afford cars with better gasoline economy cars. 4. Is the correlation between the heights of husbands and wives in the U.S. around -.9, -.3, .
3, or .9? Explain briefly. (#3. Suppose men always married women who were exactly 8%
shorter. What would the correlation between their heights be?)
4) Assuming we’re going off of problem 3, it’d be .9 because of how close the values are.
5. Three data sets are collected, and the correlation coefficient is computed in each case.
The variables are…
(i) GPA in freshman year and in sophomore year
(ii) GPA in freshman year and in senior year
(iii) length and weight of two-by-four boards
Possible values for correlation coefficients are
-.50 0.0 0.30 0.60 0.95
Match the correlations with the data sets; two will be left over. Explain your choices.
(Note-Taker’s Note: There’s literally no data given, so I’m shooting in the dark and
basing my answers off my personal experiences; your answers may and should differ)
5i) 0.60, since a year difference (aside from classes) rarely af