Suppose that in 1979 only 12% of the general adult U.S. public believed that She

Question

Suppose that in 1979 only 12% of the general adult U.S. public believed that Shell was a “premiere” company. Suppose further that you randomly selected 350 people from the general adult U.S. public this year and 25% said that Shell was a “premiere” company. If only 12% of the general adult U.S. public still believes that Shell is a “premiere” company, how likely is it that the 25% figure is a chance result in sampling 350 people? Hint: Use the techniques in this chapter to determine the probability of the 25% figure occurring by chance.

Explanation / Answer

Hint: Use the techniques in this chapter to determine the probability of the 25% figure occurring by chance.

Take 25% as the sample proportion(p1) and 12% as the population proportion(P0), n=350

std. dev. s = sqrt(P0(1 - P0)/n) = sqrt(0.12(0.88)/350) = 0.0173699

z = (p1 - P0)/s = (0.25 - 0.12)/0.0173699 = 7.484201

The two-tailed P value is less than 0.0001

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