a.
b. For each additional year of age, the height (in cm) is predicted to increase by 6.36 cm.
c. We would expect the residual for 5.5 to be in the same general area as the residuals for 4, 5, 6, and 7
(circled on the graph). The residuals in this area are all positive actual – predicted > 0 actual >
predicted. The prediction would probably be too small.
a. It is an observational study. The researcher made no attempt to impose a treatment on the subjects
in the study. The hired person simply observed and recorded behavior.
b. • The article made no mention of the sample size. Without that you are unable to judge how much
sampling variability there might have been. It’s possible that the 63–59 split was attributable to
sampling variability.
• The study was done at one Scorebucks, on one morning, for a single 2-hour period. The
population at that Scorebucks might differ in some significant way from the patrons at other
Scorebucks around the city (and there are many, many of them). It might have been different on
a different day or during a different time of the day. A single 2-hour period may not have been
enough time to collect sufficient data (we don’t know because the sample size wasn’t given)
and, again, a 2-hour period in the afternoon might have yielded different results.
c. You would conduct the study at multiple Scorebucks, possibly blocking by location if you believe
that might make a difference (i.e., would a working-class neighborhood have different
preferences than the ritziest neighborhood?). You would observe at different times of the day
and on different days. You would make sure that the total sample size was large enough to
control for sampling variability (replication).
- From the information given, we have
• P (hit the first and hit the second) = (0.4) (0.7) = 0.28
• P (hit the first and miss the second) = (0.4) (0.3) = 0.12
• P (miss the first and hit the second) = (0.6) (0.4) = 0.24
• P (miss the first and miss the second) = (0.6) (0.6) = 0.36
This information can be summarized in the following table: