A Methods and Measurements Analyst Needs to Develop a Time

Multiple Choice

A methods and measurements analyst needs to develop a time standard for a certain task. In a preliminary study, he observed one of his workers perform this task five times, with the following results: $$\begin{array} { | l | c | c | c | c | c | } \hline \text { Observation } & 1 & 2 & 3 & 4 & 5 \\\hline \text { Time(Seconds) } & 84 & 76 & 80 & 84 & 76 \\\hline\end{array}$$ How many observations should be made if the analyst wants to be 99.74 percent confident that the maximum error in the observed time is two seconds? Assume that the standard deviation of the task time is four seconds.

A)  5
B)  6
C)  25
D)  36
E)  49