The following example presents a problem with similar data structure where
the target of investigation is a possible relationship between a woman’s age and
her systolic blood pressure.
Example 2.9 The data in Table 2.14 represent systolic blood pressure readings
on 15 women. We set up a work table (Table 2.15) as in Example 2.8. Using
these totals, we obtain
r¼146 ; 260 ½ð 984 Þð 2193 Þ= 15
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
½ 67 ; 954 ð 984 Þ^2 = 15 ½ 325 ; 889 ð 2193 Þ^2 = 15 q¼ 0 : 566
indicating a moderately positive association.
TABLE 2.13
xyx^2 y^2 xy
112 63 12,544 3,969 7,056
111 66 12,321 4,356 7,326
107 72 11,449 5,184 7,704
119 52 14,161 2,704 6,188
92 75 8,464 5,625 6,900
80 118 6,400 13,924 9,440
81 120 6,561 14,400 9,720
84 114 7,056 12,996 9,576
118 42 13,924 1,764 4,956
106 72 11,236 5,184 7,632
103 90 10,609 8,100 9,270
94 91 8,836 8,281 8,5541,207 975 123,561 86,487 94,322
TABLE 2.14
Age (x) SBP (y) Age (x) SBP (y)
42 130 85 162
46 115 72 158
42 148 64 155
71 100 81 160
80 156 41 125
74 162 61 150
70 151 75 165
80 156COEFFICIENTS OF CORRELATION 87