Question

For a daily airline flight between two cities, the number of pieces of checked luggage has a mean of 380 and a standard deviation of 20. What number of pieces of checked luggage is 3 standard deviations above the mean?

Answer 1

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.

Answer 2

The answer is 440 pieces of checked luggage

Explanation:

Mean = 380

Standard deviation = 20

No. of pieces of checked luggage for 1 standard deviation = 20 pieces

Therefore, Mean for 3 standard deviations above the mean = 3 × 20 = 60

Now, number of pieces of checked luggage 3 standard deviations above the mean = Mean for 1 standard deviation + Mean for 3 standard deviations above the mean

⇒ 380 + 60 = 440 pieces