To find out the standard working time for special job, following observation data is gathered.
Observation

Time (in second)

1

17

2

18

3

15

4

14

5

13

6

15

7

16

8

13

a) If the person observed worked at pace that is 80 percent of normal, and if the suitable allowance for this task is 25 percent of job time, what must be the standard time?
b) How many observations would be required to be 95% confident that the maximum error in observed time is 1 second? Suppose that the standard deviation of task time is 2 seconds.
c) How many observations would be required to be 99 % confident that the maximum error is 5% of observed time? Suppose that the standard deviation of task time is 2 seconds. What are the formulas to solving such problems? Thanks