Listed below are the arrival delay times (in minutes) of randomly selected airpl

Question

Listed below are the arrival delay times (in minutes) of randomly selected airplane flights from one airport to another. Negative values correspond to flights that arrived early before the scheduled arrival time, and positive values represent lengths of delays. Find the range, variance, and standard deviation for the set of data. Some of the sample values are negative, but can the standard deviation ever be negative?

-28, -33, 11, -33, -9, 14, -5

range is 47 minutes.

The variance of the sample data is ______ ??

Explanation / Answer

Range = highest - lowest = 14 - (-33) = 14 + 33 = 47

Mean = (-28 + (-33) + 11 + (-33) + (-9) + 14 + (-5)) / 7 = -83/7 = -11.86

Variance = ((-28 + 11.86)2 + (-33 + 11.86)2 + (11 + 11.86)2 + (-33 + 11.86)2 + (-9 + 11.86)2 + (14 + 11.86)2 + (-5 + 11.86)2) / 6 = 400.14

Standard deviation = sqrt (variance) = sqrt(400.14) = 20

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