Question 1: What is meant by SE=0.68%?
This is the standard error. Estimates of population values vary from sample to sample and therefore have a theoretical distribution, the sampling distribution. The standard error of an estimate is a measure of the variability of this distribution. The standard error is the standard deviation of the sampling distribution of the sample estimate. The standard error therefore provides information about the precision of the estimate and is used to calculate confidence intervals around the estimates. Here the value of 0.68 is the standard error of the percentage of preterm births. The units of the standard error is the same as for the sample estimate and hence is in percentage points.
Back to Exercise: Estimation, standard error and confidence intervals.
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Last updated: 27 July, 2009.