Standard Error
Standard Error is the estimated standard deviation of a statistic based on a sample. It can be estimated using the standard deviation of a variable in a sample.
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| Where: : | s.e. is the standard error of some
statistic, most often the mean
s.d is the standard deviation of a variable n is the number of cases in the sample |
For example, a sample of 100 students reports studying a mean average of 1 hour per course per day. If another sample were collected, we would expect that the mean average might be a bit higher or a bit lower. So, we want to know the range in which these means (the statistic) is estimated to occur.
The standard deviation of this sample is .25, or one-quarter of an hour. Thus, we estimate that 68% of the students (± 1 standard deviation) study between .75 and 1.25 hours per day per course.
But, since the 1 hour is from a sample, we also want to know how much that mean might range. Here the standard error of the mean indicates that means collected from a series of samples might range between between .975 and 1.025 hours in 68% of the samples. (.025 = .25/10)
