In the July 29, 2001, issue of The Journal News (Hamilton, Oh) Lynn Elber of the

Question

In the July 29, 2001, issue of The Journal News (Hamilton, Oh) Lynn Elber of the Associated Press reported on a study conducted by the Kaiser Family Foundation regarding parents' use of television set V-chips for controlling their children's TV viewing. The study asked parents who own TV's equipped with V-chips, whether they use the devices to block programs with objectionable content.

A-Suppose that we wish to use the study results to justify the claim that fewer than 20 percent of parents who own TV sets with V-chips use the devices. The study actually found that 17 percent of the parents polled used their V-chips. If the poll surveyed 1,000 parents, and if for the sake of argument we assume that 20 percent of parents who own V-chips actually use the devices (that is, p=.2), calculate the probability of observing a sample proportion of .17 or less, That is calculate P(p .17)

B-Based on the probability you computed in part a, would you conclude that fewer than 20 percent of parents who own TV set equipped with V-chips actually use the device

Explanation / Answer

Part A: Get the z score: z = (phat-p)/sqrt(p*(1-p)/N) z = (0.17-0.2)/sqrt(0.2*0.8/1000) z = -2.3717 Now use a z table to compute: p(z < -2.3717) = 0.0089 ------------------------------------------------------------------------------------------- Part B: Since that probability is extremely low, we can conclude that less than 20% actually use the chips.

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