Question

The standard normal curve shown below models the population distribution of a random variable. What proportion of the values in the population does not lie between the two z-scores indicated on the diagram?

Answer 1

P(0 ≤ z ≤ 0.85) = 0.3023 [from tables]
P(-1.2 ≤ z ≤ 0) P(0 ≤ z ≤ 1.2) = 0.3849 [from tables]
P(-1.2 ≤ z ≤ 0.85) = 0.3023 + 0.3849 = 0.6872
Required proportion = 1 - P(-1.2 ≤ z ≤ 0.85) = 1 - 0.6872 = 0.3128
Probability of .5694 to 35.2376 with an error possibility of 980.354 pretty close.