Title: Chapter 25 STOPWATCH TIME STUDY
1Chapter 25 STOPWATCH TIME STUDY
Stopwatch Time study should be preceded by a
methods analysis so the resulting standard is
ashould take time not a did take time.
2OVERVIEW
Stopwatch time study is one of the two methods
to establish a Type I time standard.
The analyst observes one or more operators
continuously and records the time taken to
accomplish a task. This is called Observed
Time Observed Time x Rating Normal Time
3OVERVIEW
Standard time (Normal time) (100/100
Allowances)
Example Observed time 0.01 hr./unit Rating
120 Normal time 0.012 hr./unit Allowances
10 Standard time (0.012 hr./unit 100/90)
0.0133hr./unit 47.88 sec/unit
4Time Study Sheets (from ERGO)
5PREPARATION
- There are basically two steps involved in
Preparation - 1. Methods Analysis
- 2. Operator Selection
6METHODS ANALYSIS
- From a productivity standpoint, supervisors of
industrial engineering department have to do job
design. - Primary Reason Done before a Time Study - to
establish a safe, productive job. - Secondary Reason To leave a permanent record of
the methods for future audits and improvements.
7METHODS ANALYSIS
The typical items that are recorded are Date
of observation (Improvement curve) Person
observed (Skills..) Person observing
(Viewpoint) Machine used (Improvement
curve) Tools used (Improvement curve) Part No.
processed etc..
8METHODS ANALYSIS
- After a good method has been established (using
checklists), the job should be broken into
Elements
9METHODS ANALYSIS
- WHY ? - Five Reasons to divide the tasks into
elements - Elements make it possible to reuse the data
- Elements permit different ratings for
different elements Machine vs manual time - Elements permit consistency checks, within the
study and between studies - Elements improve methods descriptions
- Data collection is flexible
10METHODS ANALYSIS
- After the task is broken into elements, we write
the element description on the time study form
with a description of its (End Points (EP) - also called Termination points (TP)
11OPERATOR SELECTION
- It is very important to select the right operator
for performing the time study - There are two reasons
- Rating Accuracy(average worker)
- Worker Acceptance( do the study at different
times)
12TIMING
- Timing Techniques (example)
- Videotape
- One watch, continuous
- One watch, snapback
- Three watch system
- Electronic watches
13TIMING
- Videotape
- The primary advantage is having a permanent
record of the method. - Videotaping is less intrusive so there might not
be any discrepancies. - The tape counter does not give very accurate data
as it gives continuous timing use a stopwatch. - The elements can also be performance rated
- If any dispute occurs then the tape can also be
replayed
14TIMING
- One watch, continuous
- The stop watch does not stop, it is continuously
run (Example) - As the clock never stops, there is no time
omitted and workers like that - The disadvantage is that the observer does not
know how individual elements vary and the
observer tries to read a moving target.
15TIMING
- One watch, Snapback
- As the element ends, the time is noted and the
stop is reset (set back to zero). - The advantage is that no subtraction to be done
and the observer is able to see the pattern. - If the observer is confused then he might stop
the watch. - Continuous is preferred over snapback.
16TIMING
Three-watch system As in the title there are
three watches and it is a combination of snap
back and continuous type Initially the hands of
the first watch are moving, the seconds are
stopped at some value, and the thirds are
stopped at zero. The only disadvantage is that
there are three watches.
17TIMING
- Electronic watches
- These watches can be used either the snapback
- or the continuos mode
- The key feature is that, when the user depresses
the - button, the display time is frozen while the
clock - continues timing.
- Electronic watches with a computer built into the
- board, generally have replaced the traditional
- mechanical stop watch.
18NUMBER OF OBSERVATIONS
- There are two approaches to determining the
number of observations - Statistical
- Importance of Decision
19NUMBER OF OBSERVATIONS
Statistical A time study of sequential
observations is a sample from a population of
times. The goal is to estimate the population
mean from the sample mean. To minimize the
differences between the sample and population
means, increasing the sample size is one of the
answers.
20- The number of sample size depends on three
factors - Accuracy Desired (absolute or relative)
- Confidence Desired (based on Z score)
- Data Variability (use subsample to determine)
- Calculation formula (See Box 25.1)
- -Westinghouse/ General Electric and Niebels
- approaches are in Tables 25.2 and 25.3
21NUMBER OF OBSERVATIONS
- Irregular and Foreign Observations
- Irregular element (exp. Breakdown)
- Foreign element (exp. Customized part)
22NUMBER OF OBSERVATIONS
- Recording Techniques
- Missed Readings
- Omitted Readings
- Element out of order
- Unexpected element
23RATING
Normal Pace During the time study, the observer
will rate the worker, that is, determine the
adjustment to convert the observed time to a time
that a normal, experienced worker would take
APL MPL - Expectancy
24RATING
MPL (Motivated Productivity Level) The work
pace of a motivated worker possessing sufficient
skill and effort to do the job, physically fit to
do the job after adjustment to it, and working at
an incentive pace that can be maintained day
after day without harmful effect.
25RATING
Acceptable Productivity Level (APL) The work
pace established by management or jointly by
management and labor at a level that is
considered satisfactory it is established at a
given relationship to motivated productivity
level. Expectancy is the expected level of
productivity, it is also related to allowance.
If allowance is low, expectancy discount tends to
be high and vice-versa.
26RATING TECHNIQUES
- There cannot be a set method to rate as different
tasks within an activity requires different
levels of skills and ways - All tasks cannot be rated at a same scale
- (example)
27RATING TECHNIQUES
- Pace Rating
- The observer estimates the speed and concentrate
on dynamic micromotions such as reach or move
rather than stationary like position and grasp. - Objective Rating (three steps)
- The observer rates the speed
- Observer estimates the task difficulty
- Task difficulty factor is multiplied by the
- speed to get actual pace.
28RATING PROCEDURES
- Divide the elements and take multiple readings
- Categorize mental, fine manipulative and muscular
jobs - Categorize skilled, unskilled and semi skilled
labor - Categorize time of the day
- Rating is a very specialized task and enough
training via videotapes, practice tests,
different paces etc. should be carried out before
actual assignment
29RATING TECHNIQUES
120 100 80 60 40 20 0
Estimated Pace
Cte Error
Flat Rating
Consistency
Identity Line
0 20 40 60 80 100 120
140
Actual pace