Documentation: Census 1960 (US, County & State)
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Publisher: U.S. Census Bureau
Document: Persons of Spanish Surname (Volume II, Part I - Subject Reports)
citation:
U.S. Bureau of the Census. U.S. Census of Population: 1960. Subject Reports, Persons of Spanish Surname. Final Report PC(2)-1B. U.S. Government Printing Office, Washington, D.C. 1963.
Persons of Spanish Surname (Volume II, Part I - Subject Reports)
Sample Design and Sampling Variable
Sample Design
For persons in housing units at the time of the 1960 Census, the sampling unit was the housing unit and all its occupants; for persons in group quarters, it was the person. On the first visit to-an address, the enumerator assigned a sample key letter (A, B, C, or D) to each housing unit sequentially in the order in which he first visited the' units, whether or not he completed an interview. Each enumerator was given a random key letter to start his assignment, and the order of canvassing was indicated in advance, although these Instructions allowed some latitude in the order of visiting addresses. Each housing unit which was assigned the key letter "A" was designated as a sample unit and all persons enumerated in the unit were included in the sample. In every group quarters, the sample consisted of every fourth person in the order listed.

Although the sampling procedure did not automatically insure an exact 25-percent sample of persons or housing units in each locality, the sample design was unbiased if carried through according to instructions; and, generally, for large areas the deviation from 25 percent was found to be quite small. Biases may have arisen, however, when the enumerator failed to follow his listing and sampling instructions exactly. (For discussion of 5-percent sample.)
Ratio Estimation
The statistics based on the sample of the 1960 Census returns are estimates that have been developed through the use of a ratio estimation procedure. This procedure was carried out for each of HH groups of persons in each of the smallest areas for which sample data are published.22 (For a more complete discussion of the ratio estimation procedure, see 1960 Census of Population, Volume I, Characteristics of the Population, Part 1, United States Summary.)

These ratio estimates reduce the component of sampling error arising from the variation in the size of household and achieve some of the gains of stratification in the selection of the sample, with the strata being the groups for which separate ratio estimates are computed. The net effect is a reduction in the sampling error and bias of most statistics below what would be obtained by weighting the results of the 25-percent sample by a uniform factor of four. The reduction in sampling error is trivial for some items and substantial for others. A byproduct of this estimation procedure, in general, is that estimates for this sample are consistent with the complete count with respect to the total population and for the subdivisions used as groups in the estimation procedure.
Sampling Variability
The figures from the 25-percent sample tabulations are subject to sampling variability, which can be estimated roughly from the standard errors shown in tables C and D. These tables3 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 ½ 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 text bodies.

Footnotes:
2Estimates of characteristics from the sample for a given area are produced using the formula:



where x1 is the estimate of the characteristic for the area obtained through the use of the ratio estimation procedure,
xi is the count of sample persons with the characteristic for the area in one (i) of the 44 groups,
yi is the count of all sample persons for the area in the same one of the 44 groups, and
Yi is the count of persons in the complete count for the area in the same one of the 44 groups.

3These estimates of sampling variability are based on partial information on variances calculated from a sample of "the 1960 Census results. Further estimates are being calculated and will be made available at a later date.

Table C. Rough Approximation to Standard Error of Estimated Number (25-Percent Sample)
(Range of 2 chances out of 3)

Estimated number Standard error
50 20
100 30
250 40
500 60
1,000 70
2,500 110
5,000 150
10,000 220
15,000 270
25,000 350
50,000 490



Table D. Rough Approximation to Standard Error of Estimated Percentage (25-Percent Sample)
(Range of 2 chances out of 3)
Estimated number Base of percentage
500 1,000 2,500 10,000 25,000 100,000
2 or 98 1.8 1.3 0.7 0.4 0.1 0.1
5 or 95 2.8 2.0 1.3 0.6 0.3 0.1
10 or 90 3.9 2.8 1.7 0.8 0.4 0.3
25 or 75 5.3 3.8 2.1 1.0 0.6 0.3
50 6.2 4.3 2.2 1.1 0.7 0.4


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.

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 1 shows that there are 33,158 white persons of Spanish surname living in Arizona but born in Mexico. Table C shows that the standard error for an estimate of 33,158 is about 396, which means that the chances are approximately 2 out of 3 that the results of a complete census would not differ by more than 396 from this estimated 33,158. It also follows that there is only about 1 chance in 100 that a complete census result would differ by as much as 990, that is, by about 2 ½ times the number estimated from table C.
5-percent sample
The data presented in tables A-1 and A-2 of the appendix are based on a 5-percent sample of the 1960 Census. The 5-percent sample is a subsample of the original 25-percent sample schedules. This subsample was selected on the computer using a stratified systematic sample design. The strata were made up as follows: For persons in regular housing units there were 36 strata, i.e., 9 household size groups by 2 tenure groups by 2 color groups; for persons in group quarters, there were 2 strata, i.e., the 2 color groups.

The ratio estimation procedure for the 5-percent sample was basically the same as that used for the 25-percent sample. The requirements for combining the Mf ratio estimate groups for the 5-percent sample, however, specified that the complete count in a group could not be fewer than 275 persons, or the resulting weight could not be greater than 80. (See section above on ratio estimation for the corresponding requirements for the 25-percent sample.) For a more complete discussion of the ratio estimation procedure used in the 5-percent sample, the reader is referred to 1960 Census of Population, Subject Reports, Occupation by Industry, PC(2)-7C.
Tables E and F below give rough standard errors for absolutes and percentages, respectively, for the 5-percent sample data shown in appendix tables A-1 and A-2. These tables are used in the same way as tables C and D.

Table E. Rough Approximation to Standard Error of Estimated Number (5-Eercent Sample)
(Range of 2 chances out of 3)
Estimated number Standard error
50 40
100 60
250 80
500 130
1,000 170
2,500 280
5,000 390
10,000 550
15,000 670
25,000 870
50,000 1,230


Table F. Rough Approximation to Standard Error of Estimated Percentage (5-Percent Sample)
(Range of 2 chances out of 3)

Estimated number Base of percentage
500 1,000 2,500 10,000 25,000 100,000
2 or 98 4.6 3.2 1.8 1.1 0.4 0.4
5 or 95 7.0 5.6 3.2 1.4 0.7 0.4
10 or 90 9.8 7.0 4.2 2.1 1.1 0.7
25 or 75 14.0 9.5 5.3 2.5 1.4 0.7
50 15.4 10.9 5.6 2.8 1.8 1.1