Question

13. +-6.66 points WaneFMAC7 9.5.033. My Notes IQ scores (as measured by the Stanford-Binet intelligence test) in a certain country are normally distributed with a mean of 100 and a standard deviation of 11. Find the approximate number of people in the country (assuming a total population of 323,000,000) with an IQ higher than 120. (Round your answer to the nearest hundred thousand.) people 14. 0/6.66 points | Previous Answers My Notes This exercise uses the normal probability density function and requires the use of either technology or a table of values of the standard normal distribution The cash operating expenses of the regional phone companies during the first half of 1994 were distributed about a mean of $29.96 per access line per month, with a standard deviation of $2.55. Company A's operating expenses were $28.00 per access line per month. Assuming a normal distribution of operating expenses, estimate the percentage of regional phone companies whose operating expenses were closer to the mean than the operating expenses of Company A were to the mean. (Round your answer to two decimal places.) 0.6212 X% Submit Answer Save Press Practice Another Version 15. +-6.76 points My Notes This exercise uses the normal probability density function and requires the use of either technology or a table of values of the standard normal distribution. The cash operating expenses of the regional phone companies during the first half of 1994 were distributed about a mean of $29.75 per access line per month, with a standard deviation of $2.35. Company N's operating expenses were $34.72 per access line per month in the first half of 1994. Estimate the percentage of regional phone companies whose operating expenses were higher than those of Company N. (Round your answer to two decimal places.)

Answer 1

13)

µ = 100       

σ = 11

right tailed

P ( X ≥120)

  

Z =(X - µ ) / σ = (120.00-100) / 11=1.818

  

P(X ≥120.000) = P(Z ≥1.818) =P ( Z <-1.818) = 0.0345

excel formula for probability from z score is =NORMSDIST(Z)

so, approximate number of people = 323000000*0.0345 = 11149370.201098

or 11150000 people

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