1. CEN3722 Human Computer Interaction Human Factors Dr. Ron Eaglin

2. Objectives Define the term human factors, and describe its goals Describe general design considerations for human- machine systems. Define the term allocation of function Describe various considerations involved in the allocation of functions in human-machine systems

3. Objectives Describe the term Anthropometry Describe the following terms: Descriptive statistic Population and sample Percentile Distribution Describe various design strategies using anthropometric data

4. Human Factors Ergonomics Broad area: study of human-machine systems HCI is a subset of human factors User interface design is a subset of HCI Goals of human factors: Develop human-machine systems that Reduces error Increases productivity Enhances safety Enhances comfort

5. Human Factors Identify problem Solutions: Equipment design Task design Environmental design Training Selection

6. Human Factors Human-machine system: An arrangement of people and machines interacting within an environment in order to achieve a set of system goals Human factors specialist tries to optimize the interaction between people and machine elements, while taking the environment into account.

7. Model 7 Info processing and decision making Perceived information Motor response for control activation Displays Internal equipment status Controls Human-Machine Interface Machine Subsystem Human Subsystem

8. Defining System Goals Before Design – Know what system is supposed to do Same as UI Design Goals may conflict Cannot meet all goals – prioritize Speedy service Frequent mail delivery Delivery to all homes Low cost Guaranteed transit time

9. Defining System Goals Ambiguity What is meant by speedy service? What is considered frequent? (every day, 3 times per week) What is considered low cost? Have specific metrics for goals

10. Defining System Goals Conflict A system that delivers to 95% of residents will incur high costs in low-density population areas, conflicts with low cost Solutions Develop cost benefit analysis for trade-offs 85% of population at $.22 a letter versus 99% of population at $.45 a letter

11. Allocation of Function Process whereby the designer decides: Which tasks (functions) should be given (allocated) to the machine subsystem, and which to the human subsystem. Some things machines do better Some things humans do better Examples...

12. Machines Precision and repeatability Fast and accurate calculations Reliable memory Tirelessness Objectivity Patience Physical robustness

13. Humans General pattern matching Creativity Exception handling Learn from experience Handle ill-defined problems Good motor skills Judgment Sense of ethics and responsibility Ability to fail gracefully Flexibility and adaptability

14. Allocation of Function HF tries to delegate (allocate) as many tasks to machine as possible. Why? Reliability of a machine can be increased more efficiently than reliability of a human. Once hardware solutions, now software solutions. Human operator left with reasonable set of tasks: No overload (too many) No underload (too few)

15. Allocation of Function Extent of allocation can be modified by human operator Automatic pilot Cruise control Systematic approach to design What inputs and outputs must be provided to satisfy system goals? What operations are required to produce a system outputs? What functions should the operator perform within the system

16. Allocation of Function Systematic approach to design What are the training and skill requirements of operators? Are the tasks demanded by the system compatible with human capabilities? What equipment interfaces does the human need to perform the job? Does the human operator help or hurt the machine subsystem, and vice versa?

17. Case Study First Japanese cars designed for Japanese people (Toyopet Crown) Later exported to US without consideration for individual differences between Japanese and Americans. American men unable to press brake pedal without simultaneously pressing either clutch or accelerator pedal. Differences in driving conditions between Japan and US – could not be operated at high speeds for extended periods without mechanical damage.

18. Case Study Telecomm company built a system for presenting pre- recorded messages by telephone at times specified by the user Hardware was specified HF had to develop a mini-computer language so the user could enter appropriate commands Computer Scientists selected to create the language

19. Case Study After several months had a powerful yet elegant language Tested on secretaries (primary users) None of the secretaries were able to carry out the task Decided they needed better documentation Re-test showed secretaries still couldn’t do the task Secretaries had no computer programming experience Language was similar to traditional CP language

20. Anthropometry “Anthropos” meaning Man, and “metron” meaning to measure Scientific measurement used to better fit equipment to the human body. A goal is to obtain a set of physical measurements that accurately describes some population of users Keywords: Population: an entire set of individuals E.g., all Chinese citizens, all women United States, all Fudan University students Apply knowledge of physical measurements to design

21. Static Measures Passive measures of the dimensions of the human body. These measures are used to determine size and spacing requirements of work space. Example Measures Height Weight Wing span Seat to elbow height.

22. Dynamic Measures Measures of the dynamic properties of the human body, such as strength and endurance. Used to match the dynamic characteristics of controls to user. Measures Range of motion for joints Force of leg pushes Strength of fingers

23. Population and Samples Seldom feasible to obtain measurements from everyone in the population If entire population is small and available, best to use population data: NO ERROR. Use sampling instead A sample is a subset of individuals selected from a specific population Should be representative of population

24. Populations and Samples A “descriptive statistic” is a number that describes some characteristic of the population. Mean (average) height of Chinese men Mean weight of Fudan University Students Standard deviation of average weights for Chinese women

25. Descriptive Statistics Percentile Can range from 0 to 100, usually use 1 to 99 Defined as % of the population having a body dimension equal to or less than that indicated. 5’4” is 50 th percentile for height of Chinese men 50% are shorter, 50% are taller 5’4” is 35 th percentile for height of American men 35% are shorter, 65% are taller

26. Statistical Concepts Mean Normal Distribution

27. Statistical Concepts 5% percentile 5% less than this figure

28. Statistical Concepts 95% percentile 95% of population less than this amount

29. Weight (Men) 5% = 75 Mean = 150 95% = 250

30. Using Anthropometric Data Design strategies Design for the average individual Design for extreme individuals Design for a specified range of individuals by providing adjustment

31. Design for Average User There is no “average” individuals Everyone is unique in their own way Hundreds of recruits on 6 characteristics Some designs for the average individual Countertop height in American kitchens is 3 ft. No way to provide for an adjustable counter height Not economical for cabinet makers to make deviations of an inch or two Upside: designing for average person minimizes inconvenience for most

32. Design for Extreme Individual This strategy is widely used when upper and lower limits must be specified Example: height of door more critical for tall people Any height that would accommodate those at the 95% would accommodate shorter people.

33. Design for Extreme Individual Designing ladder for someone in the 99th percentile would hold someone in the 1th percentile. 250 pounds = 99% When concerned with minimum distances, if a 5th percentile can reach all controls, will be no problem for someone in the 95th percentile. 25 inches = 5%

34. Provide Adjustments Design for specified range of individuals by providing adjustments Should be used whenever economically feasible. E.g., seating (chairs, car seats) Most seating accommodates 5th to 95th percentile.

35. Objectives Define the term human factors, and describe its goals Describe general design considerations for human- machine systems. Define the term allocation of function Describe various considerations involved in the allocation of functions in human-machine systems

36. Objectives Describe the term Anthropometry Describe the following terms: Descriptive statistic Population and sample Percentile Distribution Describe various design strategies using anthropometric data