Understanding Psychology (10th Ed)

signifi cant outcome p. A-15
positive relationship p. A-15
negative relationship p. A-15
correlation coeffi cient p. A-16
3. A hypothetical set of data drawn from a sample of college 
sophomores at a university found that as the rate of caf-
feine consumption increases, the amount of sleep de-
creases. The scatterplot for these data is apt to show a 
relationship.
4. What would the value of the correlation coeffi cient be for 
the following?
a. A perfect negative relationship
b.
A perfect positive relationship
c.
No relationship
5.
If we observed a correlation coeffi cient of –.90 in Question 
3, we would probably be safe in saying that caffeine 
consumption causes lack of sleep in college students. True 
or false?
6.
The researchers in Question 3 decide to extend the fi nd-
ings they obtain from their sample of college sophomores 
to all adults. Would you accept their generalization? Why 
or why not? 
R E T H I N K
1.
For many years, cigarette manufacturers argued that be-
cause the data linking smoking and disease was correla-
tional, one could not infer that there was a causal 
connection between them and therefore no reason not to 
smoke. Did the manufacturers have a valid argument? 
How could you refute their argument?
Answers to Evaluate Questions 
1. sample, population; 
2. no, at least not at the .05 level typically 
requir
ed by psychologists who wish to claim a result is signifi
cant; 
3.
negative; 4.
a. 
2
1.00, b. 
1
1.00, c. 0; 5.
false; we cannot assume a 
causal relation, only an association; 
6. no; the sample (drawn fr
om 
college sophomores) does not r
epresent the population (all adults) 
A-18 Appendix 
Going by the Numbers: Statistics in Psychology
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