Use technology to solve the following problem: The lifetime of a certain type of automobile tire (in thousands of miles) is normally distributed with mean μ = 38 and standard deviation σ = 7. What proportion of tires have lifetimes between 36 and 46 thousand miles?

0.4859

Step-by-step explanation:

The formula for calculating a z-score is is z = (x-μ)/σ,

where x is the raw score,

μ is the population mean, and

σ is the population standard deviation.

From the question:

mean μ = 38,000

standard deviation σ = 7,000

For.

36 ( thousand miles) = 36,000

z = (x-μ)/σ

z = 36,000 - 38,000/7000

z = -0.28571

Probability value from Z-Table:

P(x = 36000) = 0.38755

For 46 thousand miles = 46,000

z = (x-μ)/σ

z = 46,000 - 38,000/7000

z =1.14286

Probability value from Z-Table:

P(x = 46000) = 0.87345

The proportion of tires that have lifetimes between 36 and 46 thousand miles is calculated as:

P(x = 46000) - P(x = 36000)

0.87345 - 0.38755

= 0.4859