1. Hardianto Iridiastadi, Ph.D.
Introduction to Human Factors/Ergonomics (HFE) “Engineering Anthropometry”
Hardianto Iridiastadi, Ph.D.

2. Introduction Variability in physical dimensions
Studied earlier in Anthoropology (study of mankind)
Interest in physical aspects (beginning of anthropometry)
Later, data are used for biomechanics investigations
The need to design workplaces to accomodate differences in body dimensions
Lifting, theater, faucets, car stereo, cigarette ad, challenger,

3. Human variation

4. Factors Affecting Anthropometrical Variation
Age
Gender
Race & Ethnic
Socio-economics
Occupation
Life style
Circadian
Secular trend
Measurement

5. Ergonomic Implications
International markets
Different target countries
Transfer of technology
Job selection
Healthy worker effect
Fit the man to the job

6. Engineering Anthropometry
“a branch of science originating from anthropology that attempts to describe the physical dimensions of the (human) body”
“anthropos” = man
“metron’ = measure

7. Types of Anthropometric Data
Physical (Static) anthropometry – which addresses basic physical dimensions of the body.
Functional anthropometry – concerned with physical dimensions of the body relevant to particular activities or tasks.
Newtonian data – body segment mass data and data about forces that can be exerted in different tasks/postures

8. Applications Tools design Consumer product design Workplace design
Interior design

9. Applied Anthropometry

10. Measurement Techniques
Positions
Standing naturally upright
Standing stretched to maximum height
Lean against a wall
Sitting upright
Lying (supine posture)
“Anatomical position” (see Kroemer et al)

11. Measurement Techniques
Some key measurement terms
Height
Breadth
Depth
Distance
Curvature
Circumference
Reach

12. Measuring Devices

15. Newer Measuring Devices
Photograph
Use of grids
Image processing techniques
Can record all three dimensional aspects
Infinite number of measurements
Drawbacks
Parallax
Body landmarks cannot be palpated

16. Newer Measuring Devices
Whole body scanner
Ergonomic center UI
$50,000 - $400,000
Hundreds of variables
Standing and
seated posture
Combined with
modeling software
(Jack, Mannequin, etc.)

17. Sample Anthropometric Data

18. Statistics Coefficient of variation Standard error of the mean (se)
Data diversity = sd/mean
CV ~ 5% (10% for strength data)
Large CV should be suspected
Standard error of the mean (se)
se = sd/√n
Useful for describing confidence interval
E.g., 95% CI = mean ± 1.96 se

19. Statistics
Means () and standard deviations () are typically reported for anthropometric data (often separated by gender)
Use of these value implicitly assumes a Normal distribution. Assumption is reasonable for most human data.
Percentiles can easily be calculated from mean and std.dev. using these formulas and/or standard statistical tables (usually z).

20. Statistics Percentile Commonly used: 5th, 95th, 50th (median)
Lower-limit dimension: the smaller the system, the more unusable by the largest user  Use high percentile
Upper-limit dimension: the bigger the system, the more unusable by smallest user  Use low percentile

21. Statistics - Standard Normal Variate
Z = (y-)/
Normally distributed with mean = 0 and variance = 1
z is N(0,1)
From tables of normal cumulative probabilities
P{z≤z(A)} = A
Example: if zA = 2, A = (two std.dev. above mean is the 97.7%-ile)
Properties of z:
zA > 0; above mean (>50%-ile)
zA = 0; at mean (50%-ile)
zA < 0; below mean (<50%-ile)

22. Normal Distribution Table

23. Percentile Example For female stature (from Table)
 = cm
 = 6.6 cm
What female stature represents the 37.5th %-ile?
From normal distribution:
z(37.5%) = -0.32
Thus, X(37.5%) =  + z
= (0.32)(6.6)
= cm

24. Anthropometric Data: Variances
To combine anthropometric dimension, need to calculate a new distribution for the combined measures, accounting also for the covariance (Cov) between measures (M = mean; S = std. dev.):
MX+Y = MX + MY
SX+Y = [SX2 + SY2 + 2Cov(X,Y)]1/2
SX+Y = [SX2 + SY2 + 2(rXY)(SX)(SY)]1/2
MX-Y = MX - MY
SX-Y = [SX2 + SY2 - 2Cov(X,Y)]1/2
SX-Y = [SX2 + SY2 - 2(rXY)(SX)(SY)]1/2
Means add, variances do not!

25. Class Activity

26. Anthropometrical Design Procedures
Determine dimensions of product which are critical for design (considering effectiveness, safety and comfort)
Determine the related body dimensions
Select user population (who will use the product or workplace)
Conduct reference study to find secondary data, if available (considering population characteristics) or conduct measurement
Select percentile

27. The “Average Human”
Anthropometric data for individuals is often estimated using stature or body weight in linear regression equations.
Ex: average link lengths as a proportion of body stature
Advantages:
Simplicity
Disadvantages:
relationships are not necessarily linear, nor the same for all individuals
Values represent averages for a portion of a specific population

28. Anthropometry in Design
Anthropometric data is most often used to specify reach and clearance dimensions.
The criterion values most often used:
Reach: 5% Female
Clearances: 95% Male
Try to accommodate as large as possible user population within constraints

29. Design Approaches Design for extremes Design for average
emphasize one 'tail' of distribution
Design for average
emphasize the center of a population distribution
Design for adjustability
emphasize that all potential users/consumers are 'equal’
Varying ranges of accommodation:
5th-95th %ile: typical
25th-75 %ile: less critical functions or infrequent use
1st - 99th %ile: more critical functions +/- low $
%ile: risk of severe outcomes

30. Design for Extremes Example: Door Height
Assuming a normal distribution
z = (X - )/
Obtain z => %-ile from stats table
What height to accommodate? (95th%-ile male)
 = 69”;  = 2.8” (from anthropometric table)
z0.95 = = (X - 69)/2.8 => X = 73.6”
Additional allowances?
Hair
Hats and shoes
Gait
Etc.

31. Examples Which design strategy should be employed?
leg clearance at a work table
finger clearance for a recessed button
height of an overhead conveyor system
grip size for a power tool
weight of a power tool
height of a conveyor
strength required to turn off an emergency valve

32. General Strategies and Recommendations
Design for Average:
Usually the worst approach: both larger and smaller users won’t be accommodated
Design for Extremes:
Clearance: use 95th percentile male
Reach: use 5th percentile female
Safety: accommodate >99% of population
Design for Adjustability
Preferred method, but range and degrees of adjustment are difficult to specify

33. Homework Working in groups:
Select a workplace near campus. Identify any ‘ergonomic mismatch’. Suggest how the workplace can be better designed from the perspective of engineering anthropometry. You should outline the design approach.
Pick a journal paper that discusses the use of anthropometric data in design. Submit a one-page summary (in Indonesian) of the paper. Also submit softcopy of the paper.