This is so confusing, please help. The president of an audio technology company is alarmed by the declining sales of the company's MP3 players.

Question

The president of an audio technology company is alarmed by the declining sales of the company's MP3 players. To better understand market trends, company employees asked 75 randomly chosen teenagers whether they currently own MP3 players; 9 answered YES, 66 answered NO. Find a 90% confidence interval for p, the proportion of teenagers who own MP3 players.

(A) 0.058<p<0.182

(B) 0.088<p<0.188

(C) 0.055<p<0.128

Answer 1

1. Find the sample proportion:

p= 9/75 = 0.12

Use 90% z-value: z^*=1.645

Standard error:

sqrt {0.12(0.88)/75} = 0.0375

Margin of error:

1. 1.645(0.0375) = 0.062

Confidence interval:

1. 0.12 +/- 0.062 = (0.058, 0.182)

Answer: (A) 0.058<p<0.182