A Manager Wants to Determine the Proportion of Time a Cashier

Multiple Choice

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