Russel-Research-Method-in-Anthropology

626 Chapter 20
Table 20.15 shows the data needed for finding the regression equation for
the raw data in table 20.14. At the bottom of table 20.15 you’ll find a shortcut
formula (Formula 20.22) for calculating Pearson’s r directly from the data in
the table.
TABLE 20.15
Computation of Pearson’s r Directly from Data in Table 20.14
INFMORT TFR
Country x y xy x 2 y 2
Armenia 26 1.70 44.20 676 2.890
Chad 112 6.07 679.84 12,544 36.845
El Salvador 32 3.17 101.44 1,024 10.049
Ghana 66 5.15 339.90 4,356 26.523
Iran 35 2.80 98.00 1,225 7.840
Latvia 18 1.25 22.50 324 1.562
Namibia 65 4.90 318.50 4,225 24.010
Panama 21 2.63 55.23 44 6.917
Slovenia 7 1.26 8.82 49 1.588
Suriname 29 2.21 64.09 841 4.884
total 411 31.14 1,732.52 25,705 123.107
N 10 x 41.1 y 3.114
r xy
nxy xy
nx 2 x2ny y2
2
Formula 20.22
The constant b is:
r xy
17,325.2 12,798.54
.943
(257,050 168,924)(1,231.07 969.7)
b 10(1,732.52)(411)(31.14) 4,526.66
10(25,705)(411) 2 88,129 0.051
and the constant a is then:
a 3,114.051(41.1) 1.018
The regression equation for any pair of scores on infant mortality (x) and TFR
(y), then, is:
y a bx 1.018.05(x)
Drawing the Regression Line
To draw the regression line in figure 20.4, find the expected y coordinate for
two of the actual data points on the independent variable, x. Choose the x val-