We already have the gaps: 16, 12, 10, 17.
The mean is 13.75. Let’s calculate the variance step by step:
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Step 1: Differences from the mean
16 − 13.75 = +2.25
12 − 13.75 = −1.75
10 − 13.75 = −3.75
17 − 13.75 = +3.25
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Step 2: Square the differences
(2.25)² = 5.0625
(−1.75)² = 3.0625
(−3.75)² = 14.0625
(3.25)² = 10.5625
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Step 3: Mean of squared differences (variance)
\frac{5.0625 + 3.0625 + 14.0625 + 10.5625}{4} = \frac{32.75}{4} = 8.1875
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The variance = 8.1875 days²
(Standard deviation would be √8.1875 ≈ 2.86 days)
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Do you want me to treat this as a population variance (what I just did) or a sample variance (divide by n−1 = 3 instead of 4)?