Pooling Sample Sizes

Pooling Sample Sizes

The panel dimension of the NLSY79 data collection permits one to cumulate sample cases for children at specified ages across survey points, thus attaining rather substantial sample sizes for those ages. Pooling in this manner also can greatly enhance the heterogeneity of the sample for specific research topics. The trade-off to this methodology is that the ability to follow a particular age cohort across survey years becomes somewhat limited, although it is still doable for selected research topics. Table 1 below highlights potential sample sizes using this approach.

Pooling the Child samples. From the perspective of the younger children, it is possible to attain single year of age samples numbering in the thousands for specific research efforts. For example, if one wishes to examine associations between scores on the digit span assessment and other factors for seven year olds, it would be possible to cumulate a sample of about 4,000 seven-year-old children from the first to the current assessment survey year (see Table 1 below). Because these children would have been born to mothers in all years between 1979 and 2008 (see Table 2 in the Sample Design section), the mothers of these children would range in age from their teens to their forties. The relevance of this pooling approach for evaluation of the child data, utilizing various assessments, is dealt with in the "Repeat Assessments" section of the Child Assessments--Introduction.

Pooling the Young Adults. Parallel estimates can be found for young adults. Because the young adult interviews have only been ongoing since the 1994 survey round, no single year-of-age cumulative estimate can include more than eleven points. Nonetheless, returning to Table 1 below, the number of cases cumulated in this way for ages 15 to 18 all attain single year of age totals of between 3,298 and 3,273 cases. It is worth noting that this sample cumulation modestly increases the heterogeneity of these young adult samples. For example, cumulating cases at these early young adult ages expands the age of the mothers at children's birth from mid-adolescence to the late forties. Because beginning in 2010 young adults age 31-32, 35-36, 39-40, 43-44, etc., as of December 31 of the survey year are not fielded, pooled sample sizes in these age ranges will be constrained.

Table 1. NLSY79 Child and Young Adult Sample Types for Pooled Age Groups through the Current Survey Round

Younger Children
Pooled Age Groups 1986-2014 Survey Round
Total Possible # Males Females
0 year olds 2704  1412 1292
1 year olds 3102 1586 1516
2 year olds 3280 1653 1627
3 year olds 3537 1799 1738
4 year olds 3698 1878 1820
5 year olds 3873 1989 1884
6 year olds 3909 1998 1911
7 year olds 4041 2058 1983
8 year olds 4084 2057 2027
9 year olds 4063 2056 2007
10 year olds 4137 2092 2045
11 year olds 4048 2055 1993
12 year olds 4014 2041 1973
13 year olds 3965 2021 1944
14 year olds 2242 1132 1110
 
Young Adult Children
Pooled Age Groups 1994-2014 Survey Round
Total Possible # Males Females
14 Year Olds 1863 956 907
15 Year Olds 3375 1724 1651
16 Year Olds 3463 1794 1669
17 Year Olds 3297 1640 1657
18 Year Olds 3435 1735 1700
19 Year Olds 3149 1550 1599
20 Year Olds 3222 1620 1602
21 Year Olds 2972 1451 1521
22 Year Olds 2851 1413 1438
23 Year Olds 2670 1298 1372
24 Year Olds 2633 1262 1371
25 Year Olds 2397 1213 1184
26 Year Olds 2239 1057 1182
27 Year Olds 2010 1001 1009
28 Year Olds 1855 883 972
29 Year Olds 1598 780 818
30 Year Olds 1147 540 607
31 Year Olds 350 166 184
32 Year Olds 399 162 237
33 Year Olds 752 374 378
34 Year Olds 564 288 276
35 Year Olds 121 59 62
36 Year Olds 72 34 38
37 Year Olds 210 95 115
38 Year Olds 156 79 77
39 Year Olds 40 14 26
40 Year Olds 7 3 4
41 Year Olds 18 8 10
42 Year Olds 8 6 2
       
NOTE: Ages are computed as of survey dates. For the Younger Children portion of this table, the counts are cumulative from 1986 to the current interview and are based on a child being interviewed in at least one survey year. Starting in 1994, children who are 14 at the survey date but who would reach age 15 by the end of the survey year are eligible for the Young Adult survey and are thus counted as young adults. The Young Adult Children portion of this table includes only those children who have completed at least one Young Adult survey from 1994 to the current interview. Users should note that beginning in 2010 young adults age 31-32, 35-36, 39-40, 43-44, etc, as of December 31 of the survey year are not fielded; thus, pooled sample sizes in these age ranges will be constrained.