An initial work sampling survey to estimate the percentage of time that MRI equipment is idle between 8:00 A.M. and 8:00 P.M., found that the MRI was idle in 9 of the 120 observations.
a. Determine the percentage of idle time. From the initial results, approximately how many observations would it require to estimate the actual percentage of idle time to within 4 percent, with confidence of 95 percent?