The appropriate statistical tool for this is the analysis of variance. The analysis of variance, also known as the ANOVA, is a statistical method which has the ability to separate data from observed variance into various components which is then use for more tests.
The anova gives an analysis of the differences that are in the group means of a sample.
<span>Since one standard deviation is 20 luggages, 3 standard deviations above the mean is 3*20=60 luggages above the mean of 380 luggages, so 60+380 gives the answer C, 440.</span>
