WooCommerce Post-Purchase Survey: 7 Questions, When to Ask and What to Do Next Standard deviation calculator
Enter numeric answers or metric values and get the mean, the standard deviation, the range and the coefficient of variation.
Numeric sample
Enter numbers separated by commas, spaces or new lines
Interpretation
Change the inputs to recalculate.
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How the standard deviation is calculated
Formula
Sample SD = sqrt(sum((x − mean)²) / (n − 1)). Population SD = sqrt(sum((x − mean)²) / n).
Mean
The center of the distribution that the spread is measured from.
Sample SD
Used for a sample of respondents; it divides the sum of squares by n − 1.
CV
The coefficient of variation helps compare the spread of metrics on different scales.
Calculation examples
1 Satisfaction scores
2 Support response time
What to avoid
- Ignoring outliers One extreme answer can inflate the standard deviation a lot.
- Confusing sample and population Survey data usually calls for the sample standard deviation.
- Comparing scales without the CV The SD depends on the units. For a relative comparison, use the coefficient of variation.
Frequently asked questions
How is standard deviation different from variance?
How do I know whether an SD is large or small?
Can I calculate an SD for a 1–5 scale?
What should I do with outliers?
How many values do I need?
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In SurveyNinja, NPS, CSAT and more are calculated automatically. Create a survey in 5 minutes and get real-time analytics.
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