9. The mean per capita income is 24,075 dollars per annum with a standard deviat
ID: 3321387 • Letter: 9
Question
9. The mean per capita income is 24,075 dollars per annum with a standard deviation of 536. What is the probability that the sample mean would be less than 24105 dollars if a sample of 346 persons is randomly selected? (Round your answer to 4 decimal places) (2 Points) 10. The state education commission wants to estimate the fraction of tenth grade students that have reading skills at or below the cighth grade level. In an earlier study, the population proporti required in order to estimate the fraction of tenth graders reading at or belov, the level with an error of at most 0.03? (Round your answer up to the next integer) ion was estimated to be 0.2. How large a sample would be hth grade level at the 85% confidence (2 Points) 11. Suppose that 10 scores have a bell-shaped distribution with a mean of 103 and a standard deviation of 14. Using the empirical rule, what percentage of IQ scores are between 61 and 145? (2 Points)Explanation / Answer
9) mean =24075
sd(Xbar)= s/sqrt(n)=536/sqrt(346)=28.81553
P(Xbar < 24105)
P(Z <(24105 - 24075)/28.81553)
=P(Z< 1.041105)
= 0.8511
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