It is known that undercoverage varies with age, race, and sex. Generally, undercoverage is larger for males than for females and larger for Blacks than for non-Blacks. Further, we did not adjust the independent population controls for under- coverage in the census.6 Comparability with Other Estimates. Exercise caution when comparing data from this report with data from other SIPP publications or with data from other surveys. Comparability problems are from varying seasonal patterns for many characteristics, different nonsampling errors, and different concepts and procedures.4 Sampling Variability.
Standard errors indicate the magnitude of the sampling error.
They also partially measure the effect of some nonsampling errors in response and enumeration, but do not measure any systematic biases in the data. The standard errors mostly measure the variations that occurred by chance because we surveyed a sample rather than the entire population. Uses and Computation of Standard Errors Confidence Intervals. The sample estimate and its standard error enable one to construct confidence intervals, ranges that would include the average result of alpossible samples with a known probability. Approximately 90 percent of the intervals from 1.645 standard errors below the estimate to 1.645 standard errors above the estimate would include the average result of all possible samples.