Standard Error Calculator (SEM, Proportion, Confidence Interval)

Your details

Choose how you want to supply your data.
The sample standard deviation (use the n-1 Bessel-corrected version).
Total number of observations in the sample.
Choose a confidence level to also compute the margin of error and interval bounds.
Standard Error (SE)Small sample - interpret with care
0.9

The standard error of the mean or proportion.

Sample size (n)25
Margin of error1.764
Critical value1.96
0.981.6% below · Standardised sample means (z)

Standard error: 0.9000 (n = 25)

  • With 25 observations the standard error is 0.9000, meaning the sample mean is estimated to be within roughly ±1.8000 of the true population mean in about 95% of repeated samples.
  • Your sample size (25) is below 30. The t-distribution is used for the confidence interval, which produces wider bounds than the z-distribution to account for the extra uncertainty in estimating the population spread.
  • The margin of error at the 95% level is 1.7640. Add and subtract this from your sample mean to get the confidence interval.

Next stepConsider increasing your sample size toward 30 or more to use z-based inference and tighten the confidence interval.

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