Stat 10, UCLA
Chapter 9 Solutions
- False - it's the other way round. Below-average values of the
dependent variable tend to be associated with above-average values of the
- False. For example, height in inches is usually less than weight in pounds, but the
correlation coefficient is positive.
- Height at 16 and 18; it is easier to predict 2 years ahead than 14.
- Height: environment, lifestyle, etc.. influence weight more than height.
- Age 4
False - these are cross-sectional data not longitudinal data. Younger people were born more
recently and education
levels have been going up over time.
- False: r=-0.57. The two sections that liked their TA the best did the
worst (Sections C and I)
- True: there is no pattern in the scatter diagram (r=.12)
- False: there is a moderate, positive association (r=0.46)
- True: The test takers are a self-selected group, and good students are
more likely to take the test. Hence, if a larger percentage of high
school graduates take the test, the average skill level goes down.
- False: The average in New-York is lower; but the reason may be that in
New York, a higher percentage of students take the test.
Quite a bit less because this is an ecological correlation.
- Education is measured in whole years.
- Some dots correspond to more than one couple.
- A (iv), B (iii), C (i).