8/12/2019 Sample Problems-work Sampling

1/6

SAMPLE PROBLEM

1. Given the data below, compute for the standard time :

Information Source of

Data

Data for one

day

Total time expended by operator

wor!in" time and idle time#

Time cards $%& mins

'umber of parts produced Inspection

Departmen

t

$(& pieces

)or!in" time in percent )or!

samplin"

%*+

Idle time in percent )or!

samplin"

1*+

vera"e performance index )or!

samplin"

11&+

Total allowances -ompany

timestudy

manual

1*+

wor!day#

SOLUTION :

8/12/2019 Sample Problems-work Sampling

2/6

total time in mins#xwor!in" time in +#

x performance index in percent#

Standard time / x 0

per piece Total number of pieces produced

$%& x &.%* x 1.1 1&&

/ x / 1.( mins

$(& 1&&1*#

(. n analyst has been as!ed to prepare an estimate of the

proportion of time that a lathe operator spends ad2ustin"

the machine with a 3&+ confidence level 4/1.*#. 5ased

on previous experience, the analyst believes the

proportion will be approximately 6&+. )hat sample si4e

would the analyst need in order to have the maximum

error be no more than *+7

SOLUTION :

n / 849e#2 p1p#

n / 81.*9&.&*#2

&.6&.;n / 81.*9&.&*#2 &.6&.;

n / ((%.3 or ((3

8/12/2019 Sample Problems-work Sampling

3/6

6. The owner of a lar"e "ift shop wants to estimate the

proportion of time shoppers spend in a certain part of the

store. The shop is open nine hours a day, six days a

wee!. Twelve observations will be ta!en over a 6&day

period. Determine the random observation times usin"

Table % and these instructions :

a. 0or days, read the first two di"its of column (, "oin"

down, and then the first two di"its of column 6, "oin"down.

b. 0or hours, read onedi"it numbers in row $ from left to

ri"ht.

c. 0or minutes, read numbers usin" the first two di"its in

column 1, "oin" down, and then the second two di"its in

column 1, "oin" down.

8/12/2019 Sample Problems-work Sampling

4/6

SOLUTION :

a. Days b. andom >andom >andom

number number number

;( 1 3

11 6$

($ 6 $;

1* ( 1;( 1 %*

16 * 63

;; $ ;%

16 (;

%( 1 (3

33 3 %*

1 * &*

&1 & (3

(% 1 1(

&* 31

(; 1*13 6(

&3 1&

8/12/2019 Sample Problems-work Sampling

5/6

-ombinin" these results, in the order they appeared,

produces the followin" results :

Day

8/12/2019 Sample Problems-work Sampling

6/6

rran"in" the results chronolo"ically by day, hour, and

minute but maintainin" the same combinations# produces

this list of observation times :

?bservations Day