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Under what conditions would the entire student body of your college or university be considereda population?
The entire student body of your college or university would be considered a population under any circumstances in which you want to generalize only to the student body of your school.
If the student body of your college or university were considered to be a sample, as in Exercise1.2, would this sample be random or nonrandom? Why?
The students of your college or university are a nonrandom sample of U.S. students, for example, because not all U.S. students have an equal chance of being included in the sample.
Give two examples of independent variables and two examples of dependent variables.
- Independent variables: first-grade students who attended
- kindergarten versus those who did not; seniors, masters, submasters, and juniors as categories of marathon runners.
Dependent variables: social-adjustment scores assigned by first-grade teachers; time to run 26.2 miles.
Give three examples of continuous variables.
Continuous variables: length of gestation; typing speedin words minute; and number of books in the librarycollection.
Give an example of a study in which we are interested in estimating the average score of a population.
The planners of a marathon race would like to know theaverage times of senior, master, submaster, and juniorrunners so they can plan accordingly.
Give three examples of categorical data.
(a) The number of Brown University students in anOctober 1984 referendum voting for, and the numbervoting against, the university’s stockpiling suicidepills in case of nuclear disaster.(b) The number of students in a small Midwestern collegewho are white, African-American, Hispanic-American, Asian, or other.(c) One year after an experimental program to treatalcoholism, the number of participants who are“still on the wagon,” “drinking without havingsought treatment,” or “again under treatment.”
Give an example in which the thing we are studying could be either a measurement or acategorical variable.
Children’s scores in an elementary school could bereported numerically (a measurement variable), or the studentscould be categorized as Bluebirds (Rating . 90),Robins (Rating 5 70 2 90), or Cardinals (Rating , 70).
Give an example of a variable that might be said to be measured on a ratio scale for somepurposes and on an interval or ordinal scale for other purposes.
For adults of a given height and gender, weight is aratio scale of body weight, but it is at best an ordinalscale of physical health.
What does Exercise 1.16 say about speed used as an index of motivation?
Exercise 1.16: We trained rats to run a straight-alley maze by providing positive reinforcement with food.On trial 12, a rat lay down and went to sleep halfway through the maze. What does this say about the measurement scale when speed is used as an index of learning?
Speed is probably a much better index of motivationthan of learning.
Give two examples of studies in which our primary interest is in looking at differences among groups.
(a) The final grade point average for low-achieving studentstaking courses that interest them could becompared with the averages of low-achieving studentstaking courses that do not interest them.
(b)The frequency of sexual intercourse could be comparedfor happily versus unhappily married couples.