Survey Late Night with David Letterman?

NBC asked a sample of VCR owners to record “Late Night with David Letterman” on their VCRs.


Of the 125 VCR owners surveyed, 83 either “gave up or screwed up” because they did not understand


how to program the VCR. (a) Construct a 90 percent confidence interval for the true proportion


of VCR owners who cannot program their VCRs. (b) Would viewers of this program be


typical of all television viewers? Explain.

Survey Late Night with David Letterman?
POPULATION PROPORTION, CONFIDENCE INTERVAL, NORMAL DISTRIBUTION





(a) ANSWER: 90% CONFIDENCE INTERVAL [.595, .733]


(59.5% , 73.3%) OF TRUE PROPORTION





90% CONFIDENCE INTERVAL p +/- (z critical value) * SQRT[p * (1 - p)/n]





p = POPULATION PROPORTION [0.664] (83/125)


z critical value [1.64485] (associated with 90%)


n = SAMPLE SIZE [125]





(b) Probably typical.

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