Question

2pts, 1 for work) A 2011 NBC News survey found that 80% of a sample of 4500 American teens

said they owned an MP3 player such as an ipod. Assume the sample is an SRS. Based on the

sample, the 90% confidence interval for the proportion of teens who own an MP3 player is:

a. 0.80 ± 0.0060

b. 0.80 ± 0.0117

c. 0.80 ± 0.0098

d. 0.80 ± 0.0071

3. (2pts, 1 for work) If we computed an 80% confidence interval for the previous problem, the

interval would

a. would have a smaller margin of error than the 90% confidence interval.

b. would have a larger margin of error than the 90% confidence interval.

c. could have either a smaller or a larger margin of error, it varies from sample to sample.

4. (2pts, 1 for work) How many American teens must be interviewed to estimate the proportion who

own an MP3 player within a ± 0.02 margin of error with a 99% confidence interval? Use 0.5 as

the conservative guess for p.

a. n = 1692

b. n = 2401

c. n = 4148

Answer 1

From given clata. P - o.80 n 9500 cíticol value Folle-Z010-ZDwS 1645 L.From2-table] cr: 080 4 1.6452 450D : O. 80± l,645 Co.oo59) CL Coptian@) optien A Wbuld have a Smaller mergin feror 2 .far 901, Confidence Interval. ansoer is would have a hence for thls Case Smalles margin of-error than goy、 CoofedereeTh tervd Given Margin of error CE)oo2 '.' critica] o5xll-os)(25%) value D.005 2.576 (D) 4147, 36 Somple S'se Cn)48 opten O