CEN3722 - PowerPoint Presentation

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CEN3722Human Computer InteractionTitle of Presentation

Dr. Ron EaglinSlide2

Outcomes

Explain why designers should not blame users for errors.Describe types of

errors, slips, and mistakes.

Describe the various types of

slips

.

Describe how to design to minimize errorsSlide3

OutcomesDefine and provide examples of these types of slipsCapture errors, mode errors, description errors, data-driven errors, associative-activation errors, loss of activation errors

Describe these forcing functionsGag, warn, do nothing, do what I mean, Let’s talk about it, teach me.Slide4

Consequences of Human Error1998 USSR Phobos satellite lost on trip to Mars

Ground controller omitted a single letter in a series of digital commands sent to the space craft. The omission caused code to be mistranslated to trigger a test sequence stored in ROM.

This also launched hundreds of conspiracy theorists – simply Google “Phobos UFO” Slide5

BlameEffects of electrical noise on signal reliability (well known phenomenon).Designers often use error correction codes.

If Phobos malfunction had caused Phobos loss – would ground control have been blamed?

Error correction codes were standard practice.Where is blame assigned? Slide6

FactsPeople make mistakes Creativity, adaptability, and flexibility are human strengths

Alertness and precision in action or memory are our weaknessesWe have identified class of errors and conditions likely to evoke themWe can design for error.Slide7

Humans vs. ComputersHumans deal with human errors and correct all the timeYu

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Machines need precision – do not tolerate errors wellSlide8

Dealing with ErrorsIn Design – devise systems to minimize errorsMake it easier to deal with errors

Provide clear indication of causes and remediesProvide tools to make correction easierSlide9

ExampleSlide10

ExampleOutlook 360 will prompt you to ask you ifYou mention an attachment in the body of your mail

You don’t attach an attachment to the mail.Slide11

Types of ErrorsMistakes and Slips

A person establishes an intent to act – if the intention is not appropriate this is a mistake.Misdiagnosis or misinterpretation of the situation.

Example: Incorrectly hitting send on incomplete email.If the intent is appropriate, but action is not what was intended this is a slip

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Example: a typo caused by improper hand placement on keys.Slide12

Slip – Capture ErrorDone when a frequently done activity – takes over the intended action.

Example: Turning wrong direction in car based on habit – when you intended to go other directionExample: Typing a common word incorrectly based on other words typed with a common letter sequence

Example: Typing the wrong phone number if you have one you commonly dial.Slide13

Slip – Capture Error (correction)Avoid using common sequences for infrequent commands (Such as Ctrl-C, Ctl

–V – Copy Paste)Provide feedback mechanism to tell users what they are performing (You are attempting send the message without the attachment)Have system understand the context of the commands and act/warn user accordingly.Slide14

Slips – Description ErrorHappens when there is insufficient specification of the action

Ambiguity leads to incorrect action being performedCaused by lack of consistency in command structuresSlide15

Slips - Description ErrorEnsure options a clearly differentiated (like a row of switches)

Provide sufficient feedback about action and consequenceSlips that can go unnoticed need to have feedback mechanismSlide16

Slips – Data Driven ErrorUnconscious processing of external data interferes with intention

Typing what you are thinking not what you intendedCalling your wife/child/friend by wrong name Saving file with wrong nameSlide17

Slips – Data-Driven ErrorMinimize distractions when consequences are severe

Provide clues as to intent of user (if predictable)Give suggestions for things like file name, catch obvious slipsSlide18

Slips – Loss of activation error

You forget what you are doing in mid-flowExample: talking on phone/forgetting why you calledSlide19

Slips – Loss of activation errorsUse cognitive reminders

Understand common patterns with suggestionsLists or process flows to stay on trackSlide20

Slips – Mode ErrorWhen you think you are in one state, but actually in another

Example: CAPS LOCK BEING ON AND TYPING IN ALL CAPSSlide21

Slips – Mode ErrorAvoid use of modes

Make system states are obvious, many cuesMake it easy to correct or catch“You just typed an email message in all CAPS, did you intend to do this or should I correct it?”Slide22

Design for ErrorsAnticipate human errors and prevent thenForcing Function

– prevents the behavior from continuing until the problem has been corrected.Guarantees detection but not correctionExample: disable buttons Example: Don’t allow car to lock if keys inside (require keys to lock car)Slide23

Forcing Functions - GagPrevents user from continuing if error state Computer locks unless computer and monitor are on

Car wheels locked unless key in ignitionSlide24

Forcing Functions - WarnWarning – File already exists, overwrite?

Seat belt light and audio alarmSlide25

Forcing Function – Do NothingIf action is illegal or in error – nothing happens

No user feedback, can cause frustrationSlide26

Forcing Function – Self CorrectSystem guesses legal action you want to performExample: Spell check – provides much humor on cell phones

Do What I Mean – Ultimate self correct functionSlide27

SummaryExplain why designers should not blame users for errorsDescribe common slips and mistakes and differences

Describe different types of slips and forcing functions