StatisticsdrillStandard deviation of a sum
A statistics problem from Statisticsdrill. Solve it with one answer box, with a fresh sample on every attempt and the worked steps and spreadsheet function in the answer, and it is checked the moment you submit.
The task
A job has 2 stages done one after another. Their durations are independent, with standard deviations of 2 and 12 days. What is the standard deviation of the total time? Round to 2 decimal places.
What this problem teaches
The formula: Var(X + Y) = Var(X) + Var(Y) for independent X and Y.
A hint if you get stuck
For independent quantities the variances add, not the standard deviations. Square each SD, add them, then take the square root.
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