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IQ scores are normally distributed with a mean of 100 and a standard deviation of 15 . Out of a randomly selected 1350 people from the population, how many of them would have an IQ between 95 and 123 , to the nearest whole number?

IQ scores are normally distributed with a mean of 100100 and a standard deviation of 1515 . Out of a randomly selected 13501350 people from the population, how many of them would have an IQ between 9595 and 123123 , to the nearest whole number?

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Q. IQ scores are normally distributed with a mean of 100100 and a standard deviation of 1515 . Out of a randomly selected 13501350 people from the population, how many of them would have an IQ between 9595 and 123123 , to the nearest whole number?
  1. Identify Mean and Standard Deviation: Identify the mean and standard deviation of the IQ scores.\newlineMean (μ\mu) = 100100\newlineStandard deviation (σ\sigma) = 1515
  2. Calculate Z-Scores: Calculate the z-scores for the IQ scores of 9595 and 123123. The z-score formula is z=Xμσz = \frac{X - \mu}{\sigma}, where XX is the value from the data set. For IQ = 9595: z=9510015=515=130.33z = \frac{95 - 100}{15} = \frac{-5}{15} = -\frac{1}{3} \approx -0.33 For IQ = 123123: z=12310015=23151.53z = \frac{123 - 100}{15} = \frac{23}{15} \approx 1.53
  3. Find Area Under the Curve: Use the standard normal distribution table or a calculator to find the area under the curve between the zz-scores of 0.33-0.33 and 1.531.53. The area under the curve from the mean to z=0.33z = -0.33 is approximately 0.37070.3707. The area under the curve from the mean to z=1.53z = 1.53 is approximately 0.93700.9370.
  4. Calculate Area Between Z-Scores: Calculate the area between the two z-scores by subtracting the area from the mean to z=0.33z = -0.33 from the area from the mean to z=1.53z = 1.53.\newlineArea between z=0.33z = -0.33 and z=1.53z = 1.53 = 0.93700.3707=0.56630.9370 - 0.3707 = 0.5663
  5. Find Number of People: Multiply the area by the total number of people to find the number of people with an IQ between 9595 and 123123. \newlineNumber of people == Total population ×\times Area between zz-scores \newlineNumber of people =1350×0.5663764.805= 1350 \times 0.5663 \approx 764.805
  6. Round to Nearest Whole Number: Round the result to the nearest whole number, as we cannot have a fraction of a person.\newlineNumber of people 765\approx 765

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