20. The Ethan Allen tour boat capsized and sank in Lake George, New York, and 20

Question

20. The Ethan Allen tour boat capsized and sank in Lake George, New York, and 20 of the 47 passengers drowned. Based on a 1960 assumption of a mean weight of 140 lb for passengers, the boat was rated to carry 50 passengers. After the boat sank, New York State changed the assumed mean weight from 140 lb to 174 lb.

a) Given that the boat was rated for 50 passengers with an assumed mean of 140 lb, the boat had a passenger load limit of 7000 lb. Assume that the boat is loaded with 50 male passengers and assume that weights or men are normally distributed with a mean of 182.9 lb and a standard deviation of 40.8 lb. Find the probability that the boat is overloaded because the 50 male passengers have a mean greater than 140 lb.

b) The boat was later rated to carry only 14 passengers, and the load limit was changed to 2436 lb. If 14 passengers are all males, find the probability that the boat is overloaded because their mean weight is greater than 174 lb (so that their total is greater than the maximum capacity of 2436 lb). Do the new ratings appear to be safe when the boat is loaded with 14 male passengers?

***PLEASE SHOW CALCULATOR SHORT CUT***

Explanation / Answer

X - N(182.9,40^2) , n= 50

X_bar - ( 182.9 . 40^2 / 50)

P(X_bar > 140)

P(Z > (140-182.9)/(40/sqrt(50))

=P(Z> -7.5837202)

= 1

b) P(X_bar > 174)

here n = 14

P(Z>  (174-182.9)/(40/sqrt(14))

P(Z>-0.8325)

=0.7974

Using Calculator

2) option is normalcdf

normalcdf (lower bound, upper bound, mean, standard deviation)

normalcdf(140,10^99,182.9 ,sqrt( 40^2 / 50))

for b)part

normalcdf(174,10^99,182.9 ,sqrt( 40^2 / 14))

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