Question

Xis normally distributed with mean 1,000 and standard deviation 250. What is the probability that X lies between 800 and 1, 100?

Answer 1

0.4435

Explanation:

Given that :

X is normally distributed:

mean(m) = 1,000

standard deviation (s) = 250

probability that X lies between 800 and 1,100?

Using the relation :

X = 800

Zscore = (x - m) / s

Zscore = (800 - 1000) / 250

Zscore = - 200 / 250

Zscore = - 0.8

P(Z ≤ - 0.8) = 0.2119

X = 1100

Zscore = (x - m) / s

Zscore = (1100 - 1000) / 250

Zscore = 100 / 250

Zscore = 0.4

P(Z ≤ 0.4) = 0.6554

P(Z ≤ 0.4) - P(Z ≤ - 0.8)

0.6554 - 0.2119

= 0.4435