Question

Problem #2: IQs are known to be normally distributed with mean 100 and standard deviation 15. (a) What percentage of people have an IQ lower than 90? (b) Fill in the blank. 75% of the population have an IQ that is greater than NOTE: Do not use the first half of the normal table (i.e., page 742 in the textbook, with negative z-values) because it will not be provided with the tests. Problem =2(a): Enter your answer as a percentage, correct to 2 decimals, without the % sign. e.g., 28.31 Problem #2(b): answer correct to 2 decimals Just Save Submit Problem #2 for Grading Attempt #2 Attempt #3 Attempt #4 Attempt #5 Attempt #6 Attempt #7 Attempt #8 Attempt Problem #2 Attempt #1 Your Answer: 2a) 2(a Your Mark:

Answer 1

Giveno Stana . iOS are known to be normally distributed with Meaus (H) = 100 Standard deviatios (O) = 15 * people have an io lower than 90: Pl X290) = p (x+H < 90-100) *** = Xuhe) = P(Z <- = P(Z <-0.6667) By using standard normal ²-table we get P(x290) = 0.2524819 = 0.2525 = 25.257 percentage of people having an Id lower than 90=25.25%.

75. greate tan : of the population have an IQ we know = X- p(x>k) = 0.15 p(7 > X-) - 0.45 Here, using Standard normal taste at C =0.85, thie Critical value of 7 = -0.6745 X-100 न = -0.6745 x = -0.6745 (15) + 100 = 89.8825 x = 189.88] Hance 751 of population have an IQ that is greater than 89.88