The figures from the 5percent sample tabulations are subject to Sampling Variability, which can be estimated roughly from the standard errors shown in tables C and D below. These tables
^{3} do not reflect the effect of response variance, processing variance, or bias arising in the collection, processing, and estimation steps. Estimates of the magnitude of some of these factors in the total error are being evaluated and will be published at a later date. The chances are about 2 out of 3 that the difference due to Sampling Variability between an estimate and the figure that would have been obtained from a complete count of the population is less than the standard error. The chances are about 19 out of 20 that the difference is less than twice the standard error and about 99 out of 100 that it is less than 2 Â½ times the standard error. The amount by which the estimated standard error must be multiplied to obtain other odds deemed more appropriate can be found in most statistical textbooks.
Table C shows rough standard errors of estimated numbers up to 50,000. The relative sampling errors of larger estimated numbers are somewhat smaller than for 50,000. For estimated numbers above 50,000, however, the nonsampling errors, e.g., response errors and processing errors, may have an increasingly important effect on the total error. Table D shows rough standard errors of data in the form of percentages. Linear interpolation in tables C and D will provide approximate results that are satisfactory for most purposes.
Table C. Rough Approximation to Standard Error of Estimated Number
(Range of 2 chances out of 3)
Estimated number 
Standard error 
5percent sample 
4percent sample 
1percent sample 
50 
30 
30 
70 
100 
40 
40 
90 
250 
60 
70 
130 
500 
90 
100 
200 
1,000 
120 
130 
260 
2,500 
200 
220 
440 
5,000 
280 
310 
620 
10,000 
390 
430 
860 
15,000 
480 
530 
1,060 
25,000 
620 
680 
1,360 
50,000 
880 
970 
1,940 
Table D. Rough Approximation to Standard Error of Estimated Percentage
(Range of 2 chances out of 3)
Sample size and base of percentage 
Estimated percentage 
2 or 98 
5 or 95 
10 or 90 
25 or 75 
50 
5percent sample 

1,000 
2.3 
4.0 
5.0 
6.8 
7.8 
2,500 
1.3 
2.3 
3.0 
3.8 
4.0 
10,000 
0.8 
1.0 
1.5 
1.8 
2.0 
25,000 
0.3 
0.5 
0.8 
1.0 
1.3 
100,000 
0.3 
0.3 
0.5 
0.5 
0.8 
4percent sample 

1,000 
2.5 
4.4 
5.5 
7.5 
8.6 
2,500 
1.4 
2.5 
3.3 
4.2 
4.4 
10,000 
0.9 
1.1 
1.6 
2.0 
2.2 
25,000 
0.3 
0.6 
0.9 
1.1 
1.4 
100,000 
0.3 
0.3 
0.6 
0.6 
0.9 
1percent sample 

1,000 
5.1 
8.8 
11.0 
15.0 
17.2 
2,500 
2.9 
5.1 
6.6 
8.4 
8.8 
10,000 
1.8 
2.2 
2.2 
4.0 
4.4 
25,000 
0.7 
1.1 
1.1 
2.2 
2.9 
100,000 
0.7 
0.7 
0.7 
1.1 
1.8 
For a discussion of the Sampling Variability of medians and means and of the method for obtaining standard errors of differences between two estimates see 1960 Census of Population, Volume I, Characteristics of the Population, Part 1, United States Summary.
Illustration: Table shows that for husband wife families in central cities of Urbanized Areas, there are 38,325 heads employed as clerical and kindred workers, who were first married between 1950 and 1954 and who, at the time of their first marriage, were under 22 years old. Table is based on a 5percent sample and table C shows that for an estimate of 38,325 based on the 5percent sample, a rough approximation to the standard error is about 759. This means that the chances are about 2 out of 3 that a complete census result would not differ by more than 759 from this estimated 38,325. It also follows that there is only about 1 chance in 100 that a complete count would differ by as much as 1,898, that is, by about 2 Â½ times the number estimated from table C.