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WORK SAMPLING PROBLEMS EXAMPLE 1: Observations were conducted, and it was found that the activity, under study, occurred 1200 times; Determine the limits of accuracy and limits of error when the confidence level is 95%. SOLUTION : p = [1200 / 2 500] x 100 = 4 8 %. Substituting the value of p, & CL [ which may be taken as 2 (FOR 95%)], we get, ERROR = 4% Therefore, LIMITS OF ERROR = 48(+/-) 4 i.e. in between 52% & 44% EXAMPLE 2. A work sampling study was conducted for 100 hours in the machine shop in order to estimate the Standard Time. The total number of observations recorded was 2500. No working activity could be noticed for 400 observations. The ratio between manual and machine elements were 2: 1. Average rating factor was estimated as 1.15 and the total number of articles produced during the study period was 6000. Rest, and personal allowances may be taken as 12% of the basic time (or normal time). Find the Standard time. SOLUTION Proportion of working time = [2100/ 2500] x l00 = 84% Time taken to make one article = [100* (84/100) x (60/6000)] min = 0.84 min Out of 0.84 minute, the time related to 1. Manual labour = 0.84. x (2/3)
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Unformatted text preview: = 0.56 minutes & 2. Machine time = 0.84 x (1/3) = 0.28 minute Therefore, Normal time or Basic Time per article =Observed Time x R ating + Machine time = 0.56 x 1.15 + 0.28 =0. 924 min Standard time per article = Normal time (or Basic Time) + Allowances = 0.924 + 0.924 x (12/100) = 1.0348 min. PROBLEM 1: A car manufacturing company uses robots for its painting shop. The Company is interested in determining the idle time of the robot by work sampling application. A trial study revealed that in 100 observations, 25 number of times the robot was found to be idle. Determine how many observations would have to be needed to give a confidence level of 95% and an accuracy of 5 % in the final results. PROBLEM 2: When the study was completed in the above stated car manufacturing Company, the result indicated that a total of 3733 number of observations were needed. Test whether or not the results would be within the desired accuracy. The final observations gave the following data: Observations when robot was found to be working = 2600 Observations when robot was found to be idle = 1400...
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