uke Ranges ut 1.qu for sample mean 5. Approximate f the U.S. has an Suppose at a

Question

uke Ranges ut 1.qu for sample mean 5. Approximate f the U.S. has an Suppose at a sociologist on income below $30,000. takes a sample of from the U.S. population. a. 4pts. What is a likely range for the percentage of individuals in the sample that will have an income below $30,000? 29 quo. Obop 29 DE 30000 1000 n. D00 b. 4pts. Suppose there are 400 of 1000 (40% individuals from the U.S. population have income below $30,000, is the difference between the 29% and the observed 40% probably the result of the random variability of the survey? Why? 6. According to statistics report, a surprising number of motor vehicles are not covered by insurance. Sample results from a poll showed that 52 of 200 vehicles or 26% were not covered by insurance. a. 4pts. Make a 95% confidence interval for the percentage of motor vehicles that are not insured. 2 b. 4pts. If some vehicle company claimed that the national proportion of motor vehicles that are not covered by insurance is 30%, is this claim reasonable? Why?

Explanation / Answer

7

a-is right
b. is wrong. Sample' stdev is pop.dev/sqrt(n)
c. Yes. property of normal dist.
d. Is true. CLT

b.

For the b part, use 2 instead of 5, as 2 is the actual standard deviation

c.

So, .04 = 1.96*2/sqrt(n)
n = (1.96*2/.04)^2 , n = 9604
I don't know how teacher has writtern as 1/sqrt(N) = .05

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