Understanding Psychology (10th Ed)

 
Module 56 
Descriptive Statistics 
A-13
R E C A P / E V A L U A T E / R E T H I N K
R E C A P 
How can we assess the variability of a set of data?
• The range and standard deviation are two measures of 
variability, which is the spread, or dispersion, of scores 
in a distribution. The range is the distance between the 
largest score in a distribution and the smallest score. The 
standard deviation is an index of the extent to which the 
average score in a distribution deviates from the center 
of the distribution. (p. A-10) 
E VA LU AT E
1.
A measure of variability based solely on the distance be-
tween the most extreme scores is the
a.
Spread
b.
Standard deviation
c. Deviation score
d. Range
2.
By simply eyeing the following sets of numbers, predict 
which will have a higher standard deviation and why:
a. 6, 8, 10, 10, 11, 12, 13
b. 2, 5, 8, 11, 16, 17, 18
3.
Calculate the mean and standard deviation for sets a and 
b
in Question 2.
R E T H I N K
1. If you were interested in understanding the number of 
people living below the poverty line in the United States, 
why might the range and the standard deviation provide 
you with a better understanding of the extent of poverty 
than would measures of central tendency (the mean, me-
dian, and mode)?
 Answers to Evaluate Questions 
 
Module 57 
Measures of Variability 
A-13
1.
d; 2.
b, because the numbers ar
e more widely dispersed; 
3a.
mean 
5
10, 
standard deviation 
5
2.20; 3b.
mean 
5
11, standar
d deviation 
5
5.80