Chapter 2 Examples
1. A February 2007 Gallup Poll question asked,“In politics, as of today, do you consider yourself a Republican, a Democrat, or an Independent?” The possibleresponses were “Democrat”, “Republican”, “Independent”, “Other”, and “No Response”. What kind of variable is the response?
2. Ian Walker, a psychologist at the University of Bath,wondered whether drivers treat bicycleriders differently when they wear helmets. He riggedhis bicycle with an ultrasonic sensor that could measurehow close each car was that passed him. He then rodeon alternating days with and without a helmet. Out of2500 cars passing him, he found that when he wore his
helmet, motorists passed 3.35 inches closer to him,on average, than when his head was bare.[NY Times Dec. 10, 2006]Identify Who and What wereinvestigated and the population of interest.
3.A listing posted by the Arby’s restaurantchain gives, for each of the sandwiches it sells, the type ofmeat in the sandwich, the number of calories, and theserving size in ounces. The data might be used to assessthe nutritional value of the different sandwiches.Identify the W’s,name the variables, specify for each variable whether its use indicates that it should be treated as categorical or quantitative, and, forany quantitative variable, identify the units in which it was measured.
4.In performing research for an ecology class,students at a college in upstate New York collect data onstreams each year. They record a number of biological,chemical, and physical variables, including the streamname, the substrate of the stream (limestone, shale, ormixed), the acidity of the water (pH), the temperature(°C), and the BCI (a numerical measure of biological diversity). Identify the W’s,name the variables, specify for each variable whether its use indicates that it should be treated as categorical or quantitative, and, forany quantitative variable, identify the units in which it was measured.
Answers
1.Categorical
2. Who
—2500 cars
What
—Distance from car to bicycle
Population
—All cars passing bicyclists
3.Who
—Arby’s sandwiches
Cases
—Each sandwich is a case.
What
—Type of meat, number of calories, and serving size
When
—Not specified
Where
—Arby’s restaurants
Why
—To assess nutritional value of sandwiches
How
—Report by Arby’s restaurants
Variable
—Type of meat
Type
— Categorical
Variable
—Number of calories
Type
— Quantitative
Units
— Calories
Variable
—Serving size
Type
— Quantitative
Units
— Ounces
4.Who
—Streams
Cases
—Each stream is a case.
What
—Name of stream, substrate of the stream, acidity of the
water, temperature, BCI
When
—Not specified
Where
—Upstate New York
Why
—To study ecology of streams
How
—Not specified
Variable
—Stream name
Type
—Identifier
Variable
—Substrate
Type
— Categorical
Variable
—Acidity of water
Type
— Quantitative
Units
—pH
Variable
—Temperature
Type
— Quantitative
Units
—Degrees Celsius
Variable
—BCI
Type
— Quantitative
Units
—Not specified
As defined by
Bock, David E., Paul F. Velleman, and De Veaux Richard D. Stats: Modeling the
World. Boston:Pearson/Addison-Wesley, 2007. Print.