If 35 percent of TV viewers recalled seeing an ad for a Toyota Prius on a particular television program based on a sample of 800 viewers, the 95 percent confidence interval for this study would be between approximately _____.
A) 30 percent and 40 percent
B) 32 percent and 38 percent
C) 28 percent and 42 percent
D) 20 percent and 30 percent

Question

Quizplus · Accepted Answer

We can use the formula for confidence interval as:
CI = p ± z*(sqrt(pq/n))
where
p = sample proportion = 0.35
q = 1-p = 0.65
n = sample size = 800
z = z-score for 95% confidence level = 1.96 (from standard normal distribution table)

Plugging in the values, we get:
CI = 0.35 ± 1.96*(sqrt(0.35*0.65/800))
CI = 0.35 ± 0.032
CI = (0.318, 0.382)

Therefore, the 95% confidence interval for the proportion of TV viewers who recalled seeing an ad for Toyota Prius is approximately between 32 percent and 38 percent.

If 35 Percent of TV Viewers Recalled Seeing an Ad