Tested tool guide
Tested browser tools
Checked August 16, 2026
What Standard Deviation & Statistics Calculator does, with a checked example
Feed it a batch of numbers - quiz scores, response times, sensor readings - and it returns the standard summary statistics: count, mean, median, mode, range, variance, and standard deviation, in both the sample and population variants. Everything is computed from the values you enter, and nothing leaves the page. The most common surprise is that standard deviation comes in two flavors: dividing by n-1 (sample) or by n (population). They answer different questions, and using the wrong one is the usual source of mismatches with spreadsheets or published figures.
Worked example
A concrete input and expected output from the current implementation.
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Expected output
count 6; mean 5.67; median 5.5; mode 8; range 5; sample variance 4.27; sample standard deviation 2.07; population variance 3.56; population standard deviation 1.89
The six values sum to 34, so the mean is 34/6 = 5.67. Sorted, the list is 3, 4, 5, 6, 8, 8: the median is the average of the two middle values, (5 + 6)/2 = 5.5, and the mode is 8, the only repeated value. The squared deviations from the mean sum to about 21.33; dividing by 5 gives the sample variance 4.27, dividing by 6 gives the population variance 3.56, and the standard deviations are their square roots.