SOLUTION: Dear tutor, I have a problem reading normal distribution table that z scores is above 3.0 or less than -3.0 Thank you in advance. Q.A typical adult has an average IQ score of 1

Question 1002186: Dear tutor,
I have a problem reading normal distribution table that z scores is above 3.0 or less than -3.0 Thank you in advance.
Q.A typical adult has an average IQ score of 105 with a standard deviation of 20. If 20 randomly selected adults are given an IQ test, what is the probability that the sample mean scores will be between 85 and 125 points?
Ans.
Mx = M = 105
SDx =SD/√n = 20/ √20 = 4.4721
If X ̄ = average IQ score for 20 adults,
X ̄ ~ N(105, 4.4721)
z-score for 85 = (85-105)/4.4721 =-20/4.4721 = -4.4721 (Got this part)
Area o the left of z score -4.4721 = 0 <--- I don't see this z score on the table.....
z-score for 125 = (125-105)/4.4721 = 20/4.4721 = 4.4721 (got this part)
Area to the left of z-score 4.4721 = 1 <------ I don't see this z score on the table....

Probability that the sample mean scores will be between 85 and 125 points
= Area between z scores -4.4721 (mean score 85) and +4.4721 (mean score 125)
= Area to the left of z-score 4.4721 - Area to the left of z-score -4.4721
= 1- 0 =1
If I figure it out how to read table with this z scores I can calculate this problem. but I am not quite sure how to get the area for this z score.
Thank you so much!

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Your work is correct..
The answer is 0.9999 or 1
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Cheers,
Stan H.
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