The Rowntown Cab Company has 26 cabs. The local manager wants to conduct a work sampling study to determine what proportion of the time a cab driver is sitting idle, which he estimates is about 30%. The cabs were observed at random during a five-day period by the dispatcher, who simply called each cab and checked on its status. The manager wants the estimate to be within ±3% of the proportion, with a 95% level of confidence.
a. Determine the sample size for this work sampling study.
b. The results of the first 20 observations of the work sampling study are shown as follows.

What is the revised estimate of the sample size based on these initialresults?

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Observation Idle Cabs Observation ldle Cabs 12 13 14 15 16 17 19 20 10