Statistical Methods for Psychology

78 Chapter 3 The Normal Distribution

15

Sample from normal distribution

Sample from normal distribution

Q-Q plot for normal sample

Q-Q plot for nonnormal sample

10

6

4

2

Frequency

0

15

12

10

8

6

4

2

Frequency

0

–3 –2 –1^012

X values obtained quantiles

Expected quantiles

(^3) –2 –1 021
–1^012
X values
3
obtained quantiles
–2 –1^021
–2
–1
0
1
2
Expected quantiles
–1
1
0
2
3
Figure 3.10 Histograms and Q-Q plots for normal and nonnormal data
Observed Value
80
60
40
20
Expected Normal Value
20 40 60 80
Normal Q-Q Plot of Total Behavior Problems
Figure 3.11 Q-Q plot of Total Behavior Problem scores