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Variance and standard deviation
This test develops calculation and interpretation of the mean, variance and standard deviation. Tasks compare data spread, examine the effect of outliers and assess whether a sample reliably represents a population.
Questions: 10Estimated time: 18 minutes
Time left: 00:00:00
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Top 10 registered students. Only each student’s best result in the period counts.
Sample questions
- Find the mean of: ___.
- Calculate the population variance of: ___.
- The variance is ___. Find the standard deviation.
- The variance is ___. The value ___ is added to every observation. What is the new variance?
- Standard deviation is ___. Every value is multiplied by ___. What is the new standard deviation?
Variance and standard deviation
Variance is the mean of the squared deviations of data values from their mean. Standard deviation is the square root of variance, so it has the same units as the original data.
Interpreting spread
Find the mean, each deviation, its square and the mean of those squares. A small standard deviation indicates values clustered closer to the mean. Compare both centre and spread, and check whether the required formula is for a complete population or a sample.
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