Rating & allowances

Rating Concept

Rating and Normal Performance

Operators aren’t machines. They don’t run at one fixed speed all day long—and honestly, no one does. Pace shifts. Sometimes it’s physical tiredness creeping in. Other times it’s mental—focus drops or maybe the work just feels heavier. Even small things like changes in method or the work environment can throw off the rhythm.

Because of this, a work-study engineer has to stay sharp and watch for two things in particular:

Any change from the established method
Any change in the working speed

Sounds simple, but it’s not always obvious in real time.

These variations matter. A lot. If they’re missed, the assigned rating won’t really reflect how the operator is performing. And then the whole evaluation starts to drift off track.

Definition of Normal Performance

So, what does normal performance actually mean?

At its core, it’s the pace of an average worker doing the job under fairly standard conditions. Nothing extreme. Nothing artificial. Just real, everyday working conditions, like:

Proper and capable supervision
No pressure from incentives or wage-related push
A steady, sustainable pace

Not a sprint. Not a slow crawl either.

The idea is pretty practical—this level of performance should be something a trained worker can keep up, day after day, without feeling completely drained. No burnout. No strain building up in the background.

In short, normal performance is about consistency. A balanced effort. The kind of pace that holds up over time, not just for an hour... but across entire shifts, weeks, even longer.

How the Rating Factor Is Used

Understanding Rating Levels

If an operator is observed to be working less effectively than the standard pace, the work-study engineer assigns a rating below 100 (e.g., 75, 80).
If the operator works faster and more effectively, the engineer assigns a rating above 100.

Most operators’ ratings typically fall within the range of 60 to 125. Beyond these boundaries, rating accuracy becomes unreliable.

Performance Rating Formula:

\text{Performance Rating} = \left( \frac{\text{Observed Performance}}{\text{Normal Performance}} \right) \times 100

Examples of Standard Rating

A widely accepted example of “standard pace” comes from UK and US benchmark studies:

A person of average build walking on level ground at 4 miles per hour (6.4 km/h).
Standard rate activity: Dealing 52 playing cards in 0.375 minutes.

These practical benchmarks help evaluators visualize what a 100% performance pace looks like.

Methods of Rating

Several methods exist for evaluating operator performance. The important ones include:

Speed Rating
Westinghouse System of Rating
Synthetic Rating
Objective Rating
Physiological Evaluation of Performance Rating

Speed Rating

Speed rating is probably the most widely used way to evaluate performance in work measurement. At its core, it’s pretty straightforward—it looks only at how fast the operator is working compared to what’s considered a normal pace.

The evaluator basically watches the job, compares the operator’s speed to a mental benchmark of 100% performance and then assigns a number. Maybe it’s 80 if the pace feels slow. Maybe 120 if it’s noticeably quick.

That number isn’t just for show. It’s used to adjust the observed time and convert it into Basic Time—the time the task should take if done at a normal, steady pace.

What Speed Rating Measures

Here’s the thing—speed rating doesn’t try to judge everything. It’s not about how skilled the worker is or whether the method is perfect. It zooms in on one piece only: pace.

Specifically, it looks at:

Movement speed
Rhythm
Tempo
Flow of activities
Overall work pace

That’s it.

So the real question behind speed rating is simple:
How fast is this job being done compared to normal?

Why Speed Rating Matters

Without speed rating, raw time study data doesn’t tell the full story. You might record a time, sure—but was the operator rushing? Slowing down? Working at a reasonable pace? There’s no way to know just from the stopwatch.

That’s where speed rating comes in—it fills in the gap.

It helps to:

Normalize performance differences between operators
Keep things fair, whether someone is naturally fast or a bit slower
Convert observed time into accurate Basic Time
Support proper Standard Time calculation
Maintain consistency across different studies (and even different observers)

The Concept Behind Speed Rating

The speed rating method is built on the assumption that the observer possesses a clear understanding of 100% normal performance. This is typically described as:

A steady, smooth and consistent pace
Not rushed, not slow
Sustainable over an 8‑hour day
Without undue fatigue

Examples traditionally used in work study:

A person walking 4 miles per hour (6.4 km/h)
Dealing 52 playing cards in 0.375 minutes

These reference activities give the observer a mental benchmark.

The Rating Factor

The rating factor is the ratio:

Rating Factor = \frac{Observed Speed}{Normal Speed​}

If an operator works:

Faster than normal → Rating > 100
At normal speed → Rating = 100
Slower than normal → Rating < 100

Common rating ranges:

Performance Level	Rating Range	Meaning
Very Slow	60–75	Operator far below normal pace
Below Normal	80–95	Slightly slow
Normal	96–104	Expected pace
Above Normal	105–125	Good performance
Exceptional	130+	Rarely sustainable

How Speed Rating Is Applied

Step‑By‑Step Procedure

1. Observe the Operator

The observer visually monitors the operator’s pace, rhythm and motions for each element of the work cycle.

2. Record Observed Time

Stopwatch time for each element is recorded (OT).

3. Assign Rating Factor

The observer compares the operator’s pace to the mental normal pace and assigns a rating factor (R).

Examples:

Slow worker → 80%
Normal worker → 100%
Fast worker → 120%

4. Calculate Basic Time

Basic time normalizes the observed time:

\text{Basic Time (BT)} = OT \times \frac{R}{100}

5. Use Basic Time for Further Calculations

Basic time is later used for:

Allowances
Standard Time
Line balancing
Capacity planning

Example of Speed Rating Calculation

Example 1

Observed time for an element = 0.50 minutes
Rating = 120%

B T = 0.50 \times \frac{120}{100} = 0.60 minutes

Example 2

Observed time for an element = 0.25 minutes
Rating = 80%

BT = 0.25 \times \frac{80}{100} = 0.20 \text{ minutes}

When to Use Speed Rating

Speed rating is ideal when:

The task is repetitive
Motions are smooth and predictable
The observer can clearly judge pace
There is no need to rate skill separately
A quick method is required for line efficiency improvement

It is not recommended for:

Highly skilled craft work
Irregular, long-cycle jobs
Complex manual dexterity tasks

Westinghouse Method of Rating

The Westinghouse Rating System is a widely used technique in work measurement to evaluate an operator’s performance more accurately. Instead of relying on a single judgment, it uses four separate factors to assess how effectively an operator performs a task. Each factor contributes to a composite performance rating.

The four rating factors are:

Factor	What It Measures	Description
Skill	Worker’s proficiency	Evaluates how well the operator performs the task, including coordination, technique and smoothness of movement.
Effort	Speed of applying skill	Measures the pace, energy and intensity with which the operator applies their skill to complete the task.
Consistency	Regularity of performance	Assesses how consistently the operator performs each work cycle, focusing on stability of pace and task uniformity.
Conditions	Effect of external environment	Evaluates how workplace factors—such as temperature, lighting, noise and vibrations—impact the operator’s performance.

Performance Rating Table (Westinghouse Method)
Origin: Developed by Lowry, Maynard and Stegemerten.

Skill Rating Table

Value	Grade	Category
+0.15	A1	Super skill
+0.13	A2	—
+0.11	B1	Excellent
+0.08	B2	—
+0.06	C1	Good
+0.03	C2	—
0.00	D	Average
-0.05	E1	Fair
-0.10	E2	—
-0.16	F1	Poor
-0.22	F2	—

Effort Rating Table

Value	Grade	Category
+0.13	A1	Excessive
+0.12	A2	—
+0.10	B1	Excellent
+0.08	B2	—
+0.05	C1	Good
+0.02	C2	—
0.00	D	Average
-0.04	E1	Fair
-0.08	E2	—
-0.12	F1	Poor
-0.17	F2	—

Conditions (Environmental)

Value	Grade	Category
+0.06	A	Ideal
+0.04	B	Excellent
+0.02	C	Good
0.00	D	Average
-0.03	E	Fair
-0.07	F	Poor

Consistency

Value	Grade	Category
+0.04	A	Perfect
+0.03	B	Excellent
+0.01	C	Good
0.00	D	Average
-0.02	E	Fair
-0.04	F	Poor

An observed time for an operation is 0.27 minutes and the ratings are:

Skill: Good
Effort: Excellent
Condition: Good
Consistency: Good

Performance rating factor:

Using the Westinghouse Rating Table:

Criteria	Rating	Value
Skill	C1	+0.06
Effort	B1	+0.10
Condition	C2	+0.02
Consistency	C	+0.01
Total	—	+0.19

Performance Rating Factor = 1 + 0.19 = 1.19 asic Time

Basic Time = Observed Time \times Rating Factor =0.27 \times1.19=0.3213 minutes

(Basic time represents the time a qualified operator can maintain consistently. It accounts for temporary inefficiencies and normal variations, providing a realistic standard that most trained workers can achieve with proper effort and attention)

Synthetic Rating

Based on PMTS (Predetermined Motion Time Systems), synthetic rating uses established data to determine the performance factor.

Formula for Synthetic Rating

R = \frac{P}{A}

Where:

R = Performance Rating Factor
P = Predetermined Standard Time (from PMTS)
A = Average Observed Time (from stopwatch study)

Understanding the Rating Factor

If A > P, the worker is slower than the standard → R < 1
If A = P, the worker is working at standard pace → R = 1
If A < P, the worker is faster than the standard → R > 1

Once the performance rating is obtained, it is applied to all manually controlled elements in the entire cycle.

Synthetic Rating: Exercise‑1

Problem Description

A work cycle has been divided into 8 elements and a time study has already been conducted. The average observed times of each element (in minutes) are:

Element No.	1	2	3	4	5	6	7	8
Element Type	M	M	P	M	M	M	M	M
Average Actual Time	0.14	0.16	0.30	0.52	0.26	0.45	0.34	0.15

M = Manually Controlled
P = Power Controlled

Additional Notes

Total observed cycle time = 2.32 minutes
PMTS values are available only for manual elements
We will select elements 2, 5 and 8 (all manually controlled) for rating
Using PMTS (e.g., MTM/MOST), we know the predetermined times:

Element No.	2	5	8
PMTS Time (min)	0.145	0.255	0.145

Synthetic Rating: Step‑By‑Step Calculation

Step 1: Calculate Rating Factors for Each Selected Element

Rating for Element 2:

$R_2 = \frac{0.145}{0.16} = 90.62\%$

Rating for Element 5:

$R_5 = \frac{0.255}{0.26} = 98.08\%$

Rating for Element 8:

$R_8 = \frac{0.145}{0.15} = 96.66\%$

Step 2: Average the Selected Rating Factors

$\text{Average Rating} = \frac{90.62 + 98.08 + 96.66}{3}$ $\text{Average Rating} = 95.12\% \approx 95\%$
This 95% rating factor will now be applied to all manually controlled elements in the work cycle.

Power-controlled (machine-paced) elements always receive 100% rating.

Synthetic Rating: Calculation of Normal Time

Using the rating factor table:

Element No. 1 2 3 4 5 6 7 8
Element Type M M P M M M M M
Observed Time 0.14 0.16 0.30 0.52 0.26 0.45 0.34 0.15
PMTS Time — 0.145 — — 0.255 — — 0.145
Rating Factor (%) 95 95 100 95 95 95 95 95

Basic Time Calculation

$\text{Basic Time} = 0.95(0.14+0.16+0.52+0.26+0.45+0.34+0.15) + 1.00(0.30)$ $Step‑by‑step:$
1. Sum of manual element times: 0.14+0.16+0.52+0.26+0.45+0.34+0.15 = 2.02
2. Apply rating: 0.95x2.02 = 1.92

3. Add machine‑controlled element (element 3): 1.92+0.30=2.22 minutes

Final Answer:

Basic Time=0.95x(0.14+0.16+0.52+0.26+0.45+0.34+0.15)+1.00x0.30

=2.22 minutes

$\textbf{Normal Time = 2.22 minutes}$

Why Synthetic Rating Is Superior

Synthetic rating has a bit of an edge—and once you see why, it starts to make sense why many engineers prefer it over traditional approaches.

1. Eliminates Observer Bias
No guesswork. No “this looks fast” or “that feels slow.” Synthetic rating doesn’t rely on personal judgment of pace, which means one big problem—human bias—pretty much disappears from the equation.

2. Built on Scientific Data
This isn’t based on rough observation. PMTS (Predetermined Motion Time Systems) comes from thousands of micro‑motion studies. Years of data. Tiny movements analyzed again and again. So what you’re using isn’t opinion—it’s research-backed.

3. Extremely Useful for Lean Manufacturing
Lean environments don’t like variation. Synthetic rating helps keep things tight and stable. It supports smoother operation balancing and line balancing, which is honestly where a lot of systems either work… or fall apart.

4. Ideal for Global Brands
When operations are spread across countries and factories, consistency becomes a challenge. Synthetic rating helps standardize things. Same method, same logic, same time values—no matter where the work is happening.

5. Highly Accurate for Short Cycle Tasks
Short cycles are tricky. Speed rating can struggle here because everything happens so fast. Synthetic rating handles it better. It breaks the job down to motion level, so even very quick tasks get measured properly.

In a way, it’s less about replacing traditional rating—and more about removing uncertainty where it matters most.

Objective Rating

Objective rating splits the evaluation into two stages.

Stage 1: Speed/Pace Rating

Observer records the pace of movement without considering job difficulty.

Stage 2: Job Difficulty Rating

Job difficulty is divided into six factors:

Amount of body used
Foot pedals
Bimanualness
Eye–hand coordination
Handling requirements
Weight

Each factor has adjustment percentages that modify the final basic time.

Adjustment Factor for Job Difficulty

Job difficulty adjustments are applied in Objective Rating to account for the physical and cognitive challenges involved in performing a work element. These adjustments ensure that tasks requiring more effort, precision, coordination or force receive appropriately increased basic times.

The following categories and adjustment percentages help Industrial Engineers modify performance ratings accurately.

Amount of Body Used

This factor adjusts the rating based on how much of the body is required for the task.

Reference	Condition	% Adjustment	Example
A	Fingers used loosely	0%	Fine finger movements
B	Wrist and fingers	0%	Small parts assembly
C	Elbow, wrist and fingers	0%	Light hand tools
D	Arm use	0%	Lifting small containers
E	Trunk involvement	—	Larger motions
E2	Lift with legs from floor	—	Picking up from floor level

Foot Pedals

Tasks requiring foot involvement may increase difficulty.

Reference	Condition	% Adjustment	Example
F	No pedals or pedal with fulcrum under foot	—	Typical sewing machine pedal
G	Pedal/pedals with fulcrum outside of the foot	—	Industrial machine pedal with wider rotation

Bimanualness

This measures whether one or both hands are working simultaneously.

Reference	Condition	% Adjustment	Example
H	Hands help each other	0%	Two hands holding a garment
H2	Hands work simultaneously doing duplicate operations	18%	Assembling identical components simultaneously

Eye–Hand Coordination

This factor measures visual attention and precision required.

Reference	Condition	% Adjustment	Example
I	Rough work, minimal feel	0%	Basic assembly
J	Moderate vision required	2%	Occasional peripheral vision
K	Constant but not close	4%	Standard-quality checking
L	Watchful, fairly close	7%	Close hand sewing

Handling Requirements

This measures how difficult it is to handle materials or objects.

Reference	Condition	% Adjustment	Example
M	Within 0.5 mm accuracy	10%	Precision sewing or assembly
N	Can be handled roughly	0%	No muscular force required
O	Only gross control	1%	Can squeeze or bang objects
P	Must be controlled, may need to be squeezed	2%	Delicate components
Q	Handle carefully	3%	Parts prone to damage
R	Fragile materials	5%	Glass, delicate electronics

Weight Handling

Weight or resistance directly influences job difficulty. Adjustments differ for two scenarios:

a) Arm Lift Adjustment

Weight (kg)	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0	4.5	5.0
% Adjustment	2	5	7	12	15	17	19	21	24	25

b) Leg Lift Adjustment

Weight (kg)	0.5	1.0	1.5	2.0	2.5	3.0	3.5	4.0	4.5	5.0
% Adjustment	1	1	2	3	3	4	5	7	8	10

How to Use These Adjustments

Step‑By‑Step

Identify the job element being rated.
Determine which difficulty categories apply (Amount of Body Used, Handling Requirements, etc.).
Select the correct reference condition.
Add the % adjustments from all relevant categories.
Multiply the observed time and pace rating by the final adjustment factor.

Example

If a job requires:

Hands working simultaneously (H2 → 18%)
Close eye–hand coordination (L → 7%)
Precise handling (M → 10%)
Handling 2.5 kg (Arm lift → 15%)

Total adjustment:

18 + 7 + 10 + 15 = 50\%

Adjustment factor:

1 + \frac{50}{100} = 1.50

If Observed Time = 0.40 min and Pace Rating = 110%:

Basic Time = 0.40 \times 1.10 \times 1.50 = 0.66 min

Objective Rating: Example Problem

Observed time = 0.30 minutes

Pace rating = 110%
Secondary adjustments = 120%

\text{Basic Time} = 0.30 \times 1.10 \times 1.20 = 0.396 \text{ minutes}

Element No.	1	2	3	4	5	6	7	8
Element Type	M	M	P	M	M	M	M	M
Observed Time	0.14	0.16	0.30	0.52	0.26	0.45	0.34	0.15
PMTS Time	—	0.145	—	—	0.255	—	—	0.145
Rating Factor (%)	95	95	100	95	95	95	95	95