SOLUTION: Z is a standard normal variable. Compute the requested probability when P(-.87 ≤Z≤ 2.21)

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Question 1104705: Z is a standard normal variable. Compute the requested probability when
P(-.87 ≤Z≤ 2.21)
Found 2 solutions by Boreal, jim_thompson5910:
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
This can be done from a table or a calculator.
From the calculator use 2nd VARS 2 and (-0.87,2.21)
probability is 0.7943.

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

I'm going to use this table (a similar one should be found in the back of your textbook)

Using that table, we can find the following:
P(Z < -0.87) = 0.1922 (see this image to see how I got the value)
P(Z < 2.21) = 0.9864 (see this image to see how I got the value)

So,
P(a < Z < b) = P(Z < b) - P(Z < a)
P(-0.87 < Z < 2.21) = P(Z < 2.21) - P(Z < -0.87)
P(-0.87 < Z < 2.21) = 0.9864 - 0.1922
P(-0.87 < Z < 2.21) = 0.7942 (which is the final answer)
The values are approximate