Listed below are the arrival delay times (in minutes) of randomly selected American Airline flights from New York’s JFK airport to Los Angeles (LAX). Negative values correspond to flights that arrived early before the scheduled arrival time, and positive values represent lengths of delays. (The data are from the Bureau of Transportation, and more data are listed in Data Set 15 in Appendix B.) Some of the sample values are negative, but can the standard deviation ever be negative?
-15 -18 -32 -21 -9 -32 11 2