In a workshop, three workers are doing similar continuous work, which is turning and threading a cylindrical steel bar. A work-sampling study, in this shop, was conducted over three working days. A total of 564 observations were collected. The total output, during the work-sampling period, was 270 units. The distribution of performance rate was observed as follows:
Performance rating      Frequency
100                                 41
110                                160
120                                150
130                                105
140                                  44
Q1. Assume that a confidence level of 95% and an accuracy of ±5% have been decided upon. How many random observations are needed to estimate the percentage of idle time in this work shop?
Hint: Sp =2 v{p(1-p) / N}

Q2. If total allowances are 15%, what is the standard time of producing one unit?
Hint: Standard time/unit={[(Total time) x (%working time) x (Performance Index)] / (units produced)} x [ 100/(100-Allowances)]

Q3. Assume that, each worker is paid 30 YTL/day (i.e. the minimum base wage of this class of work). In addition to that, the management of this workshop wants to motivate workers by applying the piece rate incentive system. Calculate the payment for a worker who produced 37 units/day?

Q4. If the management decided to use the standard hour plan as an incentive system, find the standard hour rate to be used in the calculation of the payments to the workers?