Practice question · Put in order
Order the steps for computing the standard deviation of a dataset.
- Subtract the mean from each value to get its deviation
- Compute the mean of the data
- Take the square root to return to the data's own units
- Average the squared deviations to get the variance
- Square each deviation
Hints
- Nothing can be measured against the centre until the centre is known.
- Squaring comes before averaging, and the root comes last.
Show the answer
- Compute the mean of the data
- Subtract the mean from each value to get its deviation
- Square each deviation
- Average the squared deviations to get the variance
- Take the square root to return to the data's own units
Why
Squaring before averaging is essential: raw deviations always average to exactly zero, since positive and negative deviations cancel. Squaring removes the cancellation, and the final square root undoes the inflation of the units.
Practise Descriptive Statistics
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