Question

The amount of fuel used by jumbo jets to take off is normally distributed with a mean of 4, 000 gallons and a standard deviation of 125 gallons. A sample of 40 jumbo jets are randomly selected. What is the probability that the mean number of gallons of fuel needed to take off for a randomly selected sample of 40 jumbo jets will be less than 3, 950 gallons?

A. 78.1%
B. 34.5%
C. 2.5%
D. 0.57%

Answer 1

given that

Mean μ= 4000 gallons

Standard deviation σ = 125 gallons

Number of trials x = 3950 gallons

What is the formula for a z-score?

Z-score = (x-μ)/σ

Z-score = (3950-4000)/125

Z-score = -0.4

So probbaility P(x<3950) = P(z<-0.4)

From the standard normal table,

P(x<3950) = 0.66