Question

Find the indicated IQ score. The graph to the right depicts IQ scores of adults, and those scores are normally distributed with a mean of 100 and a standard deviation of 15. 

The indicated IQ score is _______ . (Round to the nearest whole number as needed.)

Answer 1

Solution: Given that mean = 100, sd = 15

There fore P(X > x) = 0.3204
1 - P((X-μ)/σ <= (x-μ)/σ) = 0.3204
P((X-μ)/σ <= (x-μ)/σ) = 1 - 0.3204
P(Z <= (x-μ)/σ) = 0.6796
P(Z <= z) = 0.6796
z = 0.4666

==> NORMSINV(0.6796) = 0.4666

since, X = μ + Z*σ = 100 + 0.4666*15 = 106.999

x = 107 (nearest number)

==> The indicated IQ score is 107