The Following table is based on a time study for a metal working operation

		Obs (minutes per cycle)
Element	Performance Rating	1	2	3	4	5	5
A	108%	1.2	1.25	1.30	1.28	1.26	1.24
B	112%	0.83	0.81	0.78	0.81	0.83	0.79
C	105%	0.58	0.61	0.59	0.62	0.58	0.61

MUST SHOW ALL WORK TO RECEIVE FULL OR PARTIAL CREDIT.

a) Based on the number of observation, determine the standard time for the operation, assuming an allowance of 12 percent of job time.

b) How many observations would be needed to estimate the mean time for element B within 2 percent of its true value with a 95.5 percent confidence