Statistical Methods for Psychology

296 Chapter 10 Alternative Correlational Techniques

Table 10.1 Calculation of point-biserial correlation for

weights of males and females

Sex Weight Sex Weight

0 150 1 130

0 140 1 138

0 180 1 121

0 190 1 125

0 145 1 116

0 150 1 145

0 164 1 150

0 140 1 150

0 142 1 125

0 136 1 130

0 123 1 120

0 155 1 130

1 140 1 131

1 120

a=Y 2 bX=151.25

b=

covXY

s^2 X

=

2 5.090

(0.506)^2

= 2 19.85

r=

covXY

sXsY

=

- 5.090

(0.506)(17.792)

=-.565

covXY=-5.090

sweight=17.792

Meanweight=140.222

smale=18.869

Meanmale=151.25

ssex=0.506

Meansex=0.556

sfemale=10.979

Meanfemale=131.4

0 1

Sex

Weight

200

100

180

160

140

120

Figure 10.1 Weight as a function of Sex