A time study has been conducted on a cellular telephone assembly operation. The data shown in Table H.6 (in minutes) were obtained. A standard time within ±3 percent of the true mean with 95 percent confidence is desired.
a. Calculate the standard time for the assembly operations.
b. How many more observations will be required?

TABLE H.6 CELLULAR TELEPHONE TIME STUDY DATA OBSERVATION Work Element 1. Assemble unit 1 3 4 8 RF 0.81 0.78 0.75 0.70 0.80 0.79 0.82 0.80 1.0 1.2 2. Insert batteries 3. Test 4. Package 0.21 0.20 0.16 0.19 0.23 0.25 0.24 0.26 1.0 1.0 0.57 0.63 0.61 0.9 0.61 0.60 0.55 0.62 0.60 1.0 0.45 0.41 0.37 0.43 0.36 0.39 0.40 0.44 1.0 1.1