A work sampling study is to be made of a typist pool. It is left that typists are idle 30 % of the time. How many observations should be made in order to have 395.5% confidence so that so that the accuracy within + 4%.
Solution
Number of observation required for work sampling study=
N = c^{2} pq / E_{2}
Where c = constant depending on confidence level
P = percentage of iding q percentage of activity E = absolute error
C= 2 for 95.5% confidence level p = 0.3 , q = 1- p = 0.7, E = 4 % = 0.04
N = 4X 0.3X 0.7 / 0.04 ^{2}= 0.84 /0.0016= 525