Russel-Research-Method-in-Anthropology

Univariate Analysis 567
TABLE 19.5
Calculating the Mean for the Data in Table 19.3b
Count (f) AGE (x) fx
1 20 20
1 21 21
2 24 48
2 25 50
1 31 31
1 34 34
1 35 35
1 37 37
2 38 76
1 41 41
2 46 92
1 47 47
1 49 49
1 51 51
1 52 52
3 53 159
1 54 54
1 56 56
1 57 57
1 60 60
2 67 134
1 69 69
1 78 78
fx 1,351
fx/n 1,351/30 45.033
Calculating the Mean of Grouped Data
Table 19.6 shows the calculation of the mean for the grouped data on AGE
in table 19.4. When variable attributes are presented in ranges, as in the case
here, we take the midpoint of the range.
Note the problem in taking the mean of the grouped data in table 19.6. If
you go back to table 19.3b, you’ll see that all six of the people who are
between 20 and 29 are really between 20 and 25. Counting them all as being
25 (the midpoint between 20 and 29) distorts the mean.
Also, there are five people over 60 in this data set: one who is 60, two who
are 67, and one each who are 69 and 78. Their average age is 68.2, but they
are all counted as being just 60 in table 19.4. In calculating the mean for