Appendix A—Technical Notes: Defining and Calculating Dropout and Completion Rates Using the CPS

Event Dropout Rates

The October Supplement to the CPS is the only national data source that currently can be used to estimate annual national dropout rates. As a measure of recent dropout experiences, the event dropout rate measures the proportion of students who dropped out over a 1-year interval.

The numerator of the event dropout rate for October 2003 is the number of persons 15 through 24 years old surveyed in 2003 who were enrolled in grades 10-12 in October 2002, were not enrolled in high school in October 2003, and who also did not complete high school (that is, had not received a high school diploma or an alternative credential such as an equivalency certificate) between October 2002 and October 2003.

The denominator of the event dropout rate for 2003 is the sum of the dropouts (that is, the numerator) and all persons 15 through 24 years old who were attending grades 10-12 in October 2002, who were still enrolled in October 2003, or who graduated or completed high school between October 2002 and October 2003.

The dropout interval is defined to include the previous summer (in this case, the summer of 2003) and the previous school year (in the case of the 2002 school year), so that once a grade is completed, the student is then at risk of dropping out of the next grade. Given that the data collection is tied to each person's enrollment status in October of two consecutive years, any student who drops out and returns within the 12-month period is not counted as a dropout.

Status Dropout Rates

The status dropout rate reflects the percentage of individuals who are dropouts, regardless of when they dropped out. The numerator of the status dropout rate for 2003 is the number of individuals ages 16 through 24 years who, as of October 2003, had not completed high school and were not currently enrolled. The denominator is the total number of 16- through 24-year-olds in October 2003.

Status Completion Rates

The numerator of the high school status completion rate is the number of 18- through 24-year-olds who had received a high school diploma or an alternative credential such as an equivalency certificate. The denominator is the number of 18- through 24-year-olds who are no longer in elementary or secondary school.

High School Equivalency Credentials and the Status Completion Rate.

Prior to 2000, editions of this series of dropout reports presented estimates of overall status completion rates and estimates of the method of completion-graduation by diploma or completion by taking an alternative exam such as the General Educational Development (GED) test. Examination of the changes in the CPS GED items in the October 2000 and subsequent surveys has indicated that GED estimates for 2000 and later years are not comparable with earlier data and may not be reliable estimates of high school equivalency completions (table A-1). Therefore, CPS estimates of the method of high school completion have not been presented in recent dropout reports. Because the method of high school completion remains of interest, an estimate of those who passed the GED exam using GED Testing Service (GEDTS) data was developed.

Table A-1

Number of 18- through 24-year-olds, who received a GED, by data source: 1990 through 2002

Data on GED testing are collected by the GED Testing Service and reported in a series of annual statistical reports (American Council on Education, GED Testing Service 1996 through 2002). These reports indicate the number of people passing the GED test, by age group. Tabulation of data presented in GED Testing Service reports from 1996 through 2002 permits an estimate of the number of persons age 18-24 in 2002 (the most recent year for which data are available) who ever passed the GED test. The source data from the GEDTS reports are presented in table A-2.

GED Testing Service reports present the number of GED passers²² in the United States and the percentage of passers in each age group for persons age 16 (or age 16 and under²³), 17, 18, 19, 20-24, and higher age groups. The number of people in 2002 who were age 18-24 and who passed the GED test equals the sum of the number of people who passed the GED test since 1996 at specific ages. The GEDTS reports present grouped data for persons age 20-24. As a result, a count of the number of passers at each specific age from 20 through 24 is not available. Analysis of GEDTS data on GED passers from 2001 and 2002 indicates that approximately 8 percent of all GED passers are age 20, 6 percent are age 21, 5 percent are age 22, 4 percent are age 23, and 3 percent are age 24. It was assumed that the distribution of passers age 20-24 follows this distribution for all years from 1996 through 2002.

Table A-2

Percentage distribution of GED passers, by age group: 1996 through 2002

Data Considerations for CPS

Over the last several decades, data collection procedures, items, and data preparation processes have changed in the CPS. Some of these changes were introduced to ensure CPS estimates were comparable to decennial Census collections, some were introduced to reflect changes in the concepts under study, some were introduced to improve upon measures, and some were introduced to develop measures for new phenomena. The effects of the various changes have been studied to help ensure they did not disrupt trend data from CPS. For a summary of these studies, please see appendix C of "Dropout Rates in the United States: 2001" (Kaufman, Alt, and Chapman 2004).

CPS data include weights to help make estimates from the data representative of the civilian, noninstitutionalized population in the United States. These weights are based on decennial Census data that are adjusted for births, deaths, immigration, emigration, etc. over time. Once a decade, CPS weighting procedures shift from the previous Census to the most recent Census data. Two sets of weights are typically produced at this point; one set based on the previous Census and a second based on the most recent Census. These two sets of weights can be used to test for possible weight adjustment effects in the data. The October 2002 CPS include weights based on 1990 and 2000 Census data. To test for the possible effect of shifting from 1990-based weights to 2000-based weights, the 2002 data were weighted using both sets of weights and compared. The change in the benchmark year for the sample weights yielded no measurable difference in the event dropout, status dropout, or status completion rates for the total population, males, females, Whites, Blacks, or Hispanics (estimates not included in tables).

Imputation for Item Nonresponse in CPS.

For many key items in the October CPS, the U.S. Census Bureau imputes data for cases with missing data due to item nonresponse. However, the Census Bureau did not impute data regarding the method of high school completion before 1997. Special imputations were conducted for these items using a sequential hot deck procedure implemented through the PROC IMPUTE computer program developed by the American Institutes for Research. Three categories of age, two categories of race, two categories of sex, and two categories of citizenship were used as imputation cells.

Age and Grade Ranges in CPS Estimates.

The age and grade ranges used in the CPS measures of dropout rates are constrained by available data. Ideally, the estimates would be able to capture reliable estimates of children in grades as low as grade 9. However, the CPS asks the question about enrollment the previous October only about individuals age 15 and older. Many 9th graders are younger than age 15, so 10th grade was selected as the lower boundary of grade ranges in the event dropout rate.

Accuracy of CPS Estimates.

CPS estimates in this report are derived from samples and are subject to two broad classes of error-sampling and nonsampling error. Sampling errors occur because the data are collected from a sample of a population rather than from the entire population. Estimates based on a sample will differ somewhat from the values that would have been obtained from a universe survey using the same instruments, instructions, and procedures. Nonsampling errors come from a variety of sources and affect all types of surveys, universe as well as sample surveys. Examples of sources of nonsampling error include design, reporting, and processing errors and errors due to nonresponse. The effects of nonsampling errors are more difficult to evaluate than those that result from sampling variability. As much as possible, procedures are built into surveys in order to minimize nonsampling errors.

The standard error is a measure of the variability due to sampling when estimating a parameter. It indicates how much variance there is in the population of possible estimates of a parameter for a given sample size. Standard errors can be used as a measure of the precision expected from a particular sample. The probability that a sample statistic would differ from a population parameter by less than the standard error is about 68 percent. The chances that the difference would be less than 1.65 times the standard error are about 90 out of 100; and that the difference would be less than 1.96 times the standard error, about 95 out of 100.

Standard errors for percentages and number of persons based on CPS data were calculated using the following formulas:

Percentage:
	se =
where	p =	the percentage (0 < p < 100),
	N =	the population on which the percentage is based, and
	b =	the regression parameter based on a generalized variance formula and is associated with the characteristic. For both 2002 and 2003, b is equal to 2,131 for the total or White population; 2,410 for the Black population; and 2,744 for the Hispanic populations ages 14 through 24. For 2002, b for the Asian/Pacific Islander population ages 14 through 24 is 2,744, and in 2003 is 2,410. The b parameter for the "more than one race" population ages 14 through 24 in 2003 is 2,410. For both 2002 and 2003, the b parameter is multiplied by the following factors when calculating standard errors for regional estimates: 0.90 for the Northeast, 0.93 for the Midwest, 1.14 for the South, and 1.14 for the West.

Number of persons:
	se =
where	x =	the number of persons (i.e., dropouts),
	T =	population in the category (e.g., Blacks ages 16 through 24), and
	b =	as above.

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²² Passing the GED is a good but imperfect indicator of receiving a high school equivalency credential. Some people who pass the test may not receive the credential because they do not file necessary paperwork or pay necessary fees. People may also leave the country, die, or receive a regular high school diploma after passing the GED test.
²³ The lowest standard minimum age for testing in any state is 16. Some jurisdictions grant exceptions to the minimum age on a case-by-case basis. GED Testing Service reports from 1996-1998 group the small number of individuals under age 16 as 16 years old for reporting purposes.