Question

27) What would be the critical values of Z for 98% confidence interval for a two-tailed...

27) What would be the critical values of Z for 98% confidence interval for a two-tailed test ?

A) +/- 2.33
B) +/- 1.96
C) +/- 1.64
D) +/- 2.55

45) The I.Q. scores of 19,000 college students are approximately normally distributed with a μ = 125 and σ = 14. Find the percent of I.Q. scores that fall between 120 and 145.

Math   Statistics-And-Probability   
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Homework Answers

Answer #1

Answer 27

Based on the information provided, the significance level is α=0.02, therefore the critical value for this Two-tailed test is Zc​=2.3263. This can be found by either using excel or the Z distribution table.

Answer 28

The following information has been provided:
μ=125, σ=14

We need to compute Pr(120≤X≤145).

Therefore we get:

Hence 56.29% of IQ scores fall between 120 and 145

Excel Formula
NORM.DIST(145,125,14,TRUE)-NORM.DIST(120,125,14,TRUE)
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