Standard Deviation

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Standard Deviation
Message posted by Donna Morgan (via 198.81.16.177) on January 25, 2002 at 4:22 PM (ET)

The length of time it takes to check out at a grocery store has a mean of 4.9 minutes with a standard deviation of 2.6 minutes. A new device is invented and the result is that all checkouts at the grocery store take 30 seconds (.5 minutes) less. What is the new mean and standard deviation? I think the new mean is 4.4 minutes. Does the standard deviation stay the same?

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Re: Standard Deviation
Message posted by tom (via 68.10.228.245) on January 26, 2002 at 4:16 PM (ET)

Yes the std dev stays the same. The spread-out-ed-ness of the wait times did not change ... they only got shifted to the left by 30 seconds.

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