1. the scatterplot below shows the fuel efficiency (in
miles per gallon) and weight (in pounds) of
twenty subcompact cars.
91
3000
(a) is there a clear explanatory variable and
response variable in this setting? if so, tell
which is which. if not, explain why not.
car weight
(b) does the scatterplot show a positive association, negative association, or neither? explain why this
makes sense.
(c) how would you describe the form of the relationship?
(d) which of the following is closest to the correlation between car weight and fuel efficiency for these
20 vehicles? explain.
r=-0.9
r=-0.6
r=0 r=0.4
(e) there is one "unusual point" on the graph. explain what is "unusual" about this car.
(
what effect would removing the “unusual point” have on the correlation? justify your answer.
(g) if we converted the car weights to metric tons (1 metric ton -2,205 pounds). how would the
correlation change? explain.

An annual marathon covers a route that has a distance of approximately 26 miles. winning times for this marathon are all over 2 hours. the following data are the minutes over 2 hours for the winning male runners over two periods of 20 years each. earlier period 14 12 15 22 13 10 19 13 9 14 20 18 16 20 23 12 18 17 6 13 recent period 7 11 7 14 8 9 11 14 8 7 9 8 7 9 9 9 9 8 10 8 (a) make a stem-and-leaf display for the minutes over 2 hours of the winning times for the earlier period. use two lines per stem. (use the tens digit as the stem and the ones digit as the leaf. enter none in any unused answer blanks. for more details, view how to split a stem.) minutes beyond 2 hours earlier period 0 1 2 (b) make a stem-and-leaf display for the minutes over 2 hours of the winning times for the recent period. use two lines per stem. (use the tens digit as the stem and the ones digit as the leaf. enter none in any unused answer blanks.) minutes beyond 2 hours recent period (c) compare the two distributions. how many times under 15 minutes are in each distribution