Workshop Statistics: Discovery with Data, Second Edition

Topic 8: Graphical Displays of Association

Activity 8-1: Cars' Fuel Efficiency (cont.)

(a) observational units: cars
(b) 2 variables are recorded for each car

city MPG = quantitative
weight = quantitative

(c)

(d) Yes, it appears that cars that weigh less get better mileage than cars that weigh more.
(e) Fuel efficiency is negatively associated with weight.
(f) Yes, are several such examples, e.g. eclipse and cougar.

Activity 8-2: Guess the Association

(a) Answers will vary from student to student, but this is a good example:

¼ mile and weight: moderately negative
¼ mile and acc 0-60: very strong positive
fuel cap and page num: no real association
hwy mpg and city mpg: pretty strong positive
hwy mpg and fuel cap: pretty strong negative
front wgt and fuel cap: moderately negative
front wgt and city mpg: slight positive
city mpg and weight: strong negative
¼ mile and city mpg: moderately positive

(b) Answers will vary from student to student, but this is a good example:

length and width of signatures: positive, weak
SAT score & college G.P.A.: positive, strong
latitude & avg. January temperature of U.S. cities: negative, strong
lifetime & weekly cigarette consumption: negative, moderate
serving size & calories of fast food sandwiches: positive, weak
airfare & distance to destination: positive, moderate
birth rates & death rates of U.S. states: none, none
foot length & height: positive, strong

Activity 8-3: Marriage Ages (cont.)

(a) There is a fairly strong positive association between the husband's age and the wife's age.
(b) 2
(c) 16, above the line
(d) 5, below the line
(e) According to the data collected, the husband tends to be older than the wife in married couples.

Activity 8-4: Space Shuttle O-Ring Failures

(a)

There seems to be a slightly negative association between O-ring failures and temperature, with fewer failures at higher temperatures.
(b) It seems very likely that there would be an O-ring failure.
(c)

This scatterplot does not show any real association.
(d) The flights with zero failures gave a lot of information about how failures were related to temperature.

Activity 8-5: Fast Food Sandwiches

(a)

There is a fairly strong positive association between a sandwich's serving size and its calories. The number of calories tends to increase with the number of ounces in a serving.
(b)

Roast beef tends to have more calories than other sandwiches of similar serving sizes but different meats. Turkey tends to have less calories than other sandwiches of similar serving sizes but different meats. Ham and chicken seem to vary.

For the Calculator version, the graph is as follows:

We still see that the meat groups tend to higher calories for their serving size than the poultry groups.