IE: Human Factors

Is the "Swiss cheese model" of accidents, catastrophic system failures happen when hazard's "pass through" holes that are aligned in layers of swiss cheese slices. In this metaphor, the holes in the cheese slices represent:

Active and latent failures

All of the following are examples of conditions that could lead to a cumulative trauma disorder - with the exception of which one example here?

dangerous cutting blades which are exposed w/out hand guards

Tracking performance improves

if error feedback is made more specific

What is the Data-Ink Ratio?

keep ink which does not depict data points to a minimum

Response time=

reaction time + movement time

Which of the following is true about Cumulative Trauma Disorders?

-the are not due to a single event -they develop slowly over time - their risk increases when workers do highly repetitive work patterns

You have to build a keyboard into a device which is routinely exposed to dirt, dampness, and mud. What would be your best choice of keyboard type?

A membrane keyboard

You are designing a control which requires tracking movements using a joystick and a computer display. There are no space limitations to the control panel where this is going to be place. Given this, which of the following display types could be the best alternative and why?

A pursuit tracking display because it has better performance

Anthropometry

A. Dr. Kathleen Robinette urges engineers use fit mapping, which is using real people on prototypes and mock-ups to see who fits and who doesn't fit in the product. B. There is no average person, because no-one is at the 50th percentile for all their body dimensions C. If you cannot practically or economically design something so that people can adjust it to fit, then you can design for the average person as a compromise D. Body measurements of people in various occupations e.g electrical field worker or truck driver, can differ in important ways from the body measurements of the human population as a whole

example of conspicuity

A. Since the late 1980s, automobile brake lights were supplemented with a high center mounted brake light, which are directly in a following driver's line of sight B. One principle of warnings is that warnings should be place in an area on a device what the operators is likely to be looking at when ok loperating the device C. Self-illuminated electronic parkway road signs are bright, may have scrolling text, and are mounted over the roadway, and so catch attention D. Letters on road signs should be large enough to subtend 22-27 minutes of visual angle

Which theory of accident causation is the best (in terms of being the best in accounting for the most accidents)?

Contributing factors in accident causation (CFAC) theory

In control-display compatibility relationships, when the control is in a different plane (i.e. different physical surface) than its associated display, what can we say about that?

Control-display compatibility stereotypes will be weaker.

Which statement about traditional dynamic displays is false?

Digital displays are a good choice when values are constantly changing

When a readout of an exact numerical value is required by the operator's task, the best type of display to use is typically a ...

Digital quantitative display.

Traditional dynamic displays

- Generally, a moving pointer against a fixed scale is the preferred design - A linear (or "thermometer-like") display is preferred if the values have a natural more-less or up-down interpretation -Moving scales with a fixed pointer may be recommended if the range of values is so large as to impair the legibility of the numbers -Digital displays (counters) are preferred if an exact numeric value must be read

Esterby's design principles

- figure/ ground -figure boundary -closure -simplicity -unity

Which of these changes to a tracking task will improve performance?

- if the task has a compensatory display, replace with a pursuit display - increase the specificity of the displayed error - provide a 0.5 second preview of the input

What are the advantageous results if you design your system with compatibility (consistency with human expectations) in mind?

- learning will be faster - reaction time will be faster - fewer errors will be made - operator satisfaction will be higher

Examples of tracking

- making a turn in boat by adjusting the rubber position -steering a car while driving on the road -operating a joystick to keep cursor on a computer display in line w/ moving target -following a flying bird with binocular

Consequence of designing with control-display compatibility

- operating will invest more interest in their jobs -Performance will be more accurate (if you don't have to design with compatibility). -On the average, time to complete work tasks will be faster. -Users will comment on the designer's independence, creativity, and free spirit.

Fitt's laws

- states that the time is takes to make a pointing movement over distance D to a target of width W is a function of both distance and target width - does not apply to blind positioning (pointing movements w/ no visual feedback)

legal requirements for a warning

- text which conveys the nature of the hazard - the consequences if the warning is not heeded -what to do to reduce or eliminate the possibly of the hazard

Choice reaction time (CRT) is a response to several possible stimuli, each of which requires a different response. Which of the following factors influence choice reaction times?

- the amount of info in the stimulus - stimulus- response compatibility between display & control layout -complexity of the movement: the more complex the movement, the greater the reaction time - if a warning signal is given, CRT is faster - there is more than 1 signal, & the 2nd signal is given before the response to the 1st signal is done, then the response to the 2nd signal is delayed

movement "stereotype"

- vary in strength for different uses -are the strongest when controls & displays are in the same plane -vary by weather displays and controls are in the same or diff. planes -are examples of standardized image or conception shared by members of social group

examples of cumulative trauma disorder

-Constant daily use of a standard, straight keyboard -Repetitive use of hand tools requiring bent wrist -Extended use of a paint scraper which presses against the blood vessels of the palm -Regular use of a tool which requires overextending the thumb to activate the power button

Which of the following pieces of evidence is cited to show that there is open loop control of movements?

-more complex movements have a longer reaction time (time before the start of the actual movement), which supports the idea of motor programs, part of the open loop theory - we can execute skilled movements faster than 200 milliseconds, which is too fast to allow sensory feedback to change the movement

You presented w/ 2 rotary controls, A and B, which move a sliding pointer on a display. For a one quarter turn of control A, the pointer moves distance (shown above). For one quarter turn of control B, the pointer moves a lesser distance B. Which control has a LOWER control response ratio?

A

On the car instrument panel above, when you read the oil warning light or the battery warning light what kind of reading are you taking?

A check reading

Labels for controls should be located:

Above the control

According to Bradley (described in your book and lectures), when designing moving rotary scales with fixed pointers (such as a combination lock), there are three guidelines for display control compatibility: (1) scale should rotate in the same directions as the control knob, (2) Left-to-right movements should increase values, and (3) clockwise movement should increase values. What is true about these 3 principles?

All 3 principles are correct, but physically on 2 can be applied at any one time.

According to Norman classification of errors, there are slips and there are mistakes, a slip is

An unconscious error that happens during the execution of an automatic behavior or skill

An altimeter is a display in an airplane cockpit in which indicated the altitude at which the plane is flying. According to research discussed in the lecture and in your book, which of the above altimeter designs (A, B or C) is considered better, and why?

B because of the principle of pictorial realism

The Hick-Hyman Law

Choice reaction time (CRT) increase w/ the number of possible choices

Which statement about human performance in tracking is correct?

Compensatory tracking is more difficult than pursuit tracking.

Visual display

Complex Long Will Location in space Does not call Auditory Noisy remaining in one position

For keypads with ten keys (0-9), the telephone (1-2-3) layout is

Faster and more accurate then the calculator (7-8-9) layout

Say that you increase the resolution of your computer display, such that all your desktop icons are now smaller. You might find that it takes longer than before to move over to and click on icons around your screen (and it seems more effortful) this effort would then be an example of:

Fitt's law

Samples of a person's writing using the left hand, right hand, and mouth, & then foot are noticeably similar even though entirely different muscle groups are used in each case. This is interpreted as support for

Generalized motor programs

The demonstration that people can write reasonable handwriting when using their non-dominant hand, their lips, their elbows, and their feet illustrates which principle below?

Generalized motor programs (motor "instructions" can be generalized across situations).

According to the lecture, which statement about the visibility and/or readability of text is correct?

In general, serif letters are easier to read than sans-serif fonts - with the exception that certain specific fonts may be badly designed even though they're serif fonts.

Carpal tunnel syndrone is

Injury of the median nerve where it passes through the carpal tunnel.

What is the major problem with the Closed Loop Theory of skilled motor behavior?

It has trouble explaining movements under 200 millseconds, which are too fast for sensory feedback.

The purposed of the Bennett 'bent' handle (e.g. a bent handle on a broom) is to ...

Keep the user's wrist straight

According to a Wickens et al study (covered in your textbook), the cognitive codes a task uses (verbal versus visual) must also match the input and output modality (auditory/visual and spoken/manual) in order to provide the best performance, e.g. a visual task should use a visual display with manual control. Your book refers to this as

S-C-R compatibility SCR= stimulus- central processing response

You ask participants to increase the setting in the display up to 20 using control C, and you note that they turn clockwise. which of these principles does NOT predict that action?

Scale- side principle

The Power Law of Practice specifies that:

Speed first improves rapidly, then more slowly, but never stops improving

The graphs A and B above represent exactly the same data. Is one of these graphs better and why?

The data-ink ratio principle tells us B is better

Normal close reading distance, such as from a book, is 12-16 inches. As you move the display farther away, the letters must be enlarged. What determines the correct height of these letters?

The height is adjusted so that the visual angle is the same as close reading.

The difficulty of driving when visibility is limited by dense, thick fog, is an illustration of...

The influence of preview in tracking tasks

Which of the following is true concerning aircraft bank angle displays?

The moving aircraft or moving horizon displays can both be superior, but each one is superior under different conditions. It depends upon whether the control movements are rapidly changing or slow and steady.

When you practice a cognitive or motor skill, at first your speed and accuracy improve rapidly, but as you practice more, improvements become less and less, although you continue to improve indefinitely. This is called:

The power law of practice

Which of the following is NOT an example of tracking?

Turn a volume knob to set the desired loudness for an audio device.

Which one of the options below might be a consequence of NOT designing with control-display compatibility (consistency with human expectations) in mind?

Under conditions of fatigue or stress, the operator may revert to the "natural" or compatible response, regardless of the amount of training.

Warrick's Principle

Users expect that the point on the display will move in the same direction as the side of the control which is nearest to it - > Only applies to side placement

When we look at human performance on tracking tasks with zero, first, and second order control of the system, which two orders are most similar in performance?

Zero and first order.

according to the design principles (by Esterby).. what principle makes the above graphic symbol a good symbol?

all elements of the symbol lie w/in a single boundary

Closed loop

• Motor behavior uses sensory feedback • Must be true in the acquisition phase • Also enables precision control • Has trouble explaining fast movements

Which of these is an example of a mode error?

I cannot understand why my calculator won't give me the squarE root when I push the button with the square root symbol next to it.... Until I realize the symbol is blue so I have to press the blue button first

Assume that in the above display the operator must read the Hertz (Hz) measurement to the nearest tenth, e.g. 48.1 Hz. Given that fact, we then would say it is not optimal for human performance because it requires the operator to

Interpolate

You are designing a set of lever-style controls which are going to be placed behind the operator of a vehicle such that in normal operation the controls will not be visible to the operator. Which type of control coding would not be recommended here?

Label

Movement "stereotypes" are expectations that users have for how a display will move with respect to what direction its associated control is moved. Which statement about movement stereotypes is FALSE?

Movement stereotypes always apply universally to all humans

In Ellis & Dewar's study, which compared the speed to which participants reacted to traffic signs with symbols versus traffic signs with text-only, it was found that:

People reacted faster to symbolic traffic signs.

On the car instrument panel above, the oil warning light and the battery warning light are located close to each other. This is actually an advantage because monitoring warning lights during driving is a task requiring

Selective attention

According to lectures, alphabetic keyboards

Should not be used because of the performance disadvantage for users with any typing experience at all

Auditory presentation

Simple Short Will not Events in time Calls Visual Too bright or dark-adaptation integrity is necessary Moving about continually

Rasmussen's Skill Rules Knowledge Approach and Consciousness

Skill Based -automated rountines requiring little conscious attention Knowledge- Based -improvisation in unfamiliar environments - no routines or rules available for handing situations

In a study NOT discussed in lecture or the book, Morin & Grant (1955) had people respond to 10 lights arranged in a row by pressing 10 buttons, also arranged in a row. Responses were fastest when there was a direct correspondence between the light and button locations. What does this illustrate?

Spatial compatibility

In tracking, what are input, output, and error?

Target= input physical response= output difference between input & output = error

You have the choice in your project of creating new displays for your system from the very beginning. For one function, you have the option of choosing a visual display or an auditory display. Under which of these conditions should you prefer a visual display?

The messages are long and complex and will be referred to later.

An altimeter, a display which provides the altitude at which an airplane is flying, turns out to be best if it is a vertical linear display. This is an illustration of ...

The principle of pictorial realism.

According to the conclusions promoted in the lecture on keyboards, the best choice for a keyboard arrangement for a computer is

The standard Qwerty or Sholes keyboard.

Research has conclusively shown that human performance (speed and errors) on 10-key keypads is better with which arrangement?

The telephone (1-2-3) arrangement

The strict definition of reaction time is

The time between the onset of a signal and the initiation of a movement response.

A recent journal article reports proof that Fitt's law applies to touch screens. What does this imply?

The time it takes to rapidly move a finger from a starting point to a target on the touch screen is a function of the distance to the target and the size of the target

Performance in a tracking task becomes worse if

There is a time lag between the operator moving the control and the response of the display system

In anthropometry, we find that measurements of static dimensions can vary by the occupation that people have chosen, e.g. utility worker may have different body measurements than other professions or the population as a whole. True or False

True

Scale- side principle

Users expect that the pointer will move in the same direction as the side of the control knob which is on the same side as the scale markings on the display

Clockwise for increase principle

Users will turn a rotary control clockwise no matter where the control is located relative to the display

Which of the following is NOT one of the legal requirements for an "adequate" warning?

a graphic symbol

Extended use of a scraper tool causes tissue compression on the palm with constriction of blood flow, which can lead to numbness and eventual long-term consequences. What is this called?

carpal tunnel syndrome

Tracking

human performance on zero and first order systems are nearly the same

What is the reason that changing a straight handle on a tool is to a bent handle would be recommended?

it keeps the wrist straight (reduces ulnar deviation)

Fast movements of 200 milliseconds or less cannot be influenced by

sensory feedback

Generalized motor programs

set of motor instruction which can be generalized across situation o Invariant characteristics Independent of specific muscles Sequence and relative timing may be invariantsin a program

In order to prevent WWII pilots from retracting their landing gears and thus damaging their planes upon landing, control levels were redesigned using

shape coding

Choice reaction time (CRT)

the more stimuli, the longer the reaction time

Comparing the 2 displays above, one is considered superior

the scales should be numbered by 10s, and 20s

High sensitivity in a control knob is best when:

the system output must travel a long distance with little effort

Simples reaction time- (SRT)

time to initiate a response to a single stimulus