1. A time study observation was conducted for a bench making operation. The observed time was recorded in the following table. Use this observation to answer the questions that follow.

Element Performance 1 Rating

OBSERVATIONS (minutes per cycle)

2 3 4 5 6

0.60 0.54 0.58 0.53 0.52 1.24 1.15 1.20 1.17 1.16 0.85 0.83 0.87 0.78 No

observed

A B C

105% 0.59 110% 1.22 115% 0.82

a. Determine the standard time for the operation, assuming an allowance of 15 percent of job time.

b. How many observations would be needed to estimate the mean time for element C within 1 percent of its true value with a 95.5 percent confidence?

c. How many observations would be needed to estimate the mean time for element C within .01 minute of its true value with a 95.5 percent confidence?

2. An analyst had a need to estimate the percentage of time milling machines are idle. She therefore designed an initial survey where she found that the milling machines were idle in 6 of the 50 observations.

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16 August 2021

a. b.

Calculate the estimated idle time in percentage.

What would be the approximate number of observations required to estimate the actual percentage of idle time to within 5 percent with a confidence of 95 percent?

Operations Management IV (PRB470S) Tutorials Weighting: Part of 10% set aside for Tutorials Due: 19 August 2021 @ 23:59 A time study observation was conducted for a bench making operation. The observed time was recorded in the following table. Use this observation to answer the questions that follow OBSERVATIONS minutes per cycle) Element Performance Rating 1 2 3 4 5 6 A B C 105 110 115 0.59 1.22 0.X2 0.60 1.24 O.RS 0.54 1.15 0.83 0.5 1:20 087 0.53 1.17 0.78 0.52 1.16 Ne observed a. Determine the standard time for the operation, assuming an allowance of 15 percent of job time. b. How many observations would be needed to estimate the mean time for element within 1 percent of its true value with a 95.5 percent confidence? How many observations would be needed to estimate the mean time for element within .01 minute of its true value with a 95.5 percent confidence? An analyst had a need to estimate the percentage of time milling machines are idle. She therefore designed an initial survey where she found that the milling machines were ide in 6 of the 50 observations a. Calculate the estimated idle time in percentage. b. What would be the approximate number of observations required to estimate the actual percentage of idle time to within 5 percent with a confidence of 95 percent? 11 16 August 2021