Question

Is rap music more popular among young Indians than among young Asians? A sample survey compared 634 randomly chosen Indians aged 15 to 25 with 567 randomly selected Asians in the same age group. It found that 368 of the Indians and 130 Asians listened to rap music every day. Construct and interpret a 95% confidence interval for the difference between the proportions of black and white young people who listen to rap every day.

Answer 1

Explanation:

Confidence interval for the difference in the two proportions is written as

Difference in sample proportions ± margin of error

Sample proportion, p = x/n

Where x = number of successes

n = number of samples

For the indians,

x = 368

n1 = 634

p1 = 368/634 = 0.58

For the asians

x = 130

n2 = 567

p2 = 130/567 = 0.23

Margin of error = z√[p1(1 - p1)/n1 + p2(1 - p2)/n2]

To determine the z score, we subtract the confidence level from 100% to get α

α = 1 - 0.95 = 0.05

α/2 = 0.05/2 = 0.025

This is the area in each tail. Since we want the area in the middle, it becomes

1 - 0.025 = 0.975

The z score corresponding to the area on the z table is 1.96. Thus, confidence level of 95% is 1.96

Margin of error = 1.96 × √[0.58(1 - 0.58)/634 + 0.23(1 - 0.23)/567]

= 1.96 × √0.00038422713 + 0.00031234568)

= 0.052

Confidence interval = 0.58 - 0.23 ± 0.052

Confidence interval = 0.35 ± 0.052