Types of Variables & Data

Question 1

if a study finds that CBT is more effective for treating adolescents with social anxiety disorder when the adolescents have authoritative parents than when they have authoritarian parents, then parenting style is a (mediator/moderator)?

Answer 1

moderator

**A moderator variable affects the direction and/or strength of the relationship between independent and dependent variables. **

Question 2

match the example(s) of variables to the correct type of variable: nominal, ordinal, interval, ratio

a) Likert-type scales
b) IQ scores
c) yearly income measured in dollars
d) gender, eye color, DSM diagnosis

Answer 2

a) ordinal
b) interval
c) ratio
d) nominal

Question 3

match the type of graph with the variables typically represented in the graph: nominal, ordinal, interval, ratio

a) histograms
b) bar graphs
c) frequency polygons (aka line graphs)
d) ranks

Answer 3

a) interval & ratio variables
b) nominal & ordinal variables
c) interval & ratio variables
d) ordinal variables

Some authors recommend bar graphs for ordinal data, while others recommend histograms.

Question 4

characteristics of a normal distribution

Answer 4

1) mean, median, & mode (3 measures of central tendency) are all equal to the same value

2) 68% of scores fall between scores + or - one standard deviation from the mean; 99% of scores fall between scores + or - THREE standard deviations from the mean

e.g., if a distribution of scores on a job knowledge test for a sample of employees has a mean of 100 & SD of 10:
* 68% of employees obtained scores between 90 and 110
* about 95% obtained scores between 80 and 120
* about 99% obtained scores between 70 and 130

Question 5

characteristics of skewed distributions

Answer 5

1) either positivly or negatively skewed
2) mean, median, & mode do not equal the same value
* the mean is in the extended tail with the few scores
* the median is in the middle
* the mode is in the side of the distribution that contains most of the scores

Question 6

in a negatively skewed distribution, what is the order of the mean, median and mode from smallest to largest? what about a positively skewed distribution?

Answer 6

negatively skewed:
mean > median > mode

positively skewed:
mode > median > mean

Question 7

when a distribution is skewed, which is the preferred measure of central tendency (mean/median/mode)? Why?

Answer 7

median
* because it is not distored by the atypical scores in the distribution (unlike the mean)

Question 8

characteristics of a leptokurtic vs. platykurtic distribution

Answer 8

leptokurtic: sharper peak, flatter tail than normal distribution (most scores are “piled up” in the middle of the distribution)

platykurtic: flatter in the middle, thicker tails than a normal distribution (scores are more evently distributed throughout)