Question

The number of miles that regular tires last has a normal distribution with a mean of 50,000 miles and a standard deviation of 8,200 miles if a random sample of 4 tries are selected ,what .is the probability that means number of miles they last is more then 60,000 miles?

use this standard normal table to calculate this probability.
A.0.0025
B.0.0075
C.0.0559
D.0.9925

Answer 1

B.0.0075

Explanation:

Given that:

Mean, m = 50,000

Standard deviation, s = 8200

Sample size, n = 4

P(x > 60,000) :

Zscore = (x - m) / s÷sqrt(n)

Zscore = (60000 - 50000) / 8200 ÷2

Z = 10000 / 4100

Z = 2.4390243

P(Z > 2.439)

Using the Z probability calculator :

P(Z > 2.439) = 0.007364

This is closest to B.0.0075 in the option.