A Problem on Time Study on Sandwich Assembling at Frank’s BBQ Delight
Chapter 11, MGMT4102, J. Wang
Name __________________________
Job: Assembling the Super Chicken Sandwich.
Job elements / units, their means and SD’s of work times from 10 initial observations:
Work Elements / units
#
1
2
3
4
5
6
7
Description
Get bulkie rolls (box of 12)
Prepare bulkie roll, move to prep area, open up roll
Get barbecued chicken (4-lb. box)
Place 8 oz. chicken on roll
Spread on special BBQ sauce
Close bulkie roll, slice in half
Wrap sandwich, place in pickup area
From initial 10 observations
Mean work time (min)
Standard deviation
(x-bar)
(min) (s)
2.4
0.2
0.08
0.005
4.0
0.55
0.25
0.015
0.1
0.01
0.1
0.0125
0.15
0.01
Calculated minimum
observations (n)
Management wants that the resulted standard time of an element is within ±5% of the true mean time for 90% of confidence.
That is, a=0.05.
(1) Find value of z: z= _______________ for 90% of confidence according to Table 11-3 p.405.
(2) Calculate minimum number of observations, n, for each element and put it in the above table and the table on the next page.
Now more observations have been carried out. The mean work time after sufficient observations of each element is given in
the tale below.
Management figures out PRF (performance rating factor) and F (frequency of occurrence) for each element, and puts them in
the table below. In addition, management estimates the factor of PED (personal time, fatigue, unavoidable delay) for the worker on
this job is 0.10.
(3) The allowance factor AF for working time is this job is thus calculated as: AF=1/(1-PED) = _______________________.
Put it in the table below.
Work Elements / units
#
Description
1
2
3
4
5
6
7
Get bulkie rolls (box of 12)
Prepare bulkie roll, move to prep
area, open up roll
Get barbecued chicken (4-lb. box)
Place 8 oz. chicken on roll
Spread on special BBQ sauce
Close bulkie roll, slice in half
Wrap sandwich, place in pickup area
Sum
Number
of
observat
ions (n)
Mean work
time (min)
based on n
observations
2.2
0.1
4.25
0.2
0.1
0.12
0.12
PRF
F
1.1
0.9
0.083
1.0
0.95
1.25
1.0
0.9
1.25
0.125
1.0
1.0
1.0
1.0
Normal time
AF
Standard Time
(4) Calculate the normal time (NT) of each element and put in the table above.
(5) Calculate the standard time (ST) of each element and put in the table above.
(6) Calculate the total standard time of completing the job of assembling the super chicken sandwich.
(7) If a worker works at the standard time, how many sandwiches can this worker prepare per hour?
(8) If the manager expects demand for the sandwich to be 100 per hour, how many workers should be assigned to preparing
them?