A manager wants to determine the proportion of time a cashier is idle. A work sampling method was used, and the idle time was found to be 20 percent based on 100 observations. If the manager wants a + 0.05 with a 95 percent confidence level (z = 1.96), how many MORE observations are needed?
A) fewer than or equal to 200
B) greater than 200 but fewer than or equal to 300
C) greater than 300 but fewer than or equal to 400
D) greater than 400

Question

Quizplus · Accepted Answer

The sample size needed for a desired confidence level and precision can be calculated using the formula: n = (Z^2 * p * q) / e^2, where Z is the z-score for the desired confidence level, p is the estimated proportion, q is 1 - p, and e is the desired precision. Plugging in the given values, we get: n = (1.96^2 * 0.2 * 0.8) / 0.05^2 = 245.86. Since we need to round up to the nearest whole number, the manager needs to take 246 more observations.

A Manager Wants to Determine the Proportion of Time a Cashier