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Human Interface And Human Error Computer Science Essay

One of the largest errors and mistakes on any huge and complex computing machine systems are straight connected towards Human Interactions. Usually these mistakes occur due to the fact that the interface of a certain interface has been ill designed, but computing machine systems and companies are excessively comfy with the fact that if an mistake occurs that they need a Human to repair it. This is where the job originates. Even the most extremely trained user are prone to dullness when there is merely a demand for normal work, and anxiousness when an unfamiliar mistake occurs, emphasis degrees are elevated.

A Human Interface gives the right feedback to the user so that they have the clip to make up one’s mind on a valid manner to manage an mistake with their current informations on the system. A user is sometime prone to do a large trade out of a little mistake and so overlooks a existent menace to the system.

Experiential rating, mental walkthroughs, and experimental ratings like protocol examination are ways to find the effectivity of the Human Interface, but they do n’t ever supply conclusive informations. A System developer must see that the Human Interface is easy to understand and grok and intuitive for the users to utilize, but non so simple that it bores the user into a province of contentment and lowers his or her reactivity to mistakes that need immediate attending.


Certified that this research undertaking titled: Human Interface and Human Error is the bona fide record of work carried out by Johnathan Salmon for my concluding twelvemonth of B.

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Sc. computing machine Science.

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Technical Guide Research Coordinator Principal

Topographic point: Belgique Campus IT varsity Date: 2012/06/11

Problem Statement

In this paper I was making research in order to happen out:

What is Human Computer Interface

How does Human Error Influence it

How to work out Human Error In A Complex System


Figure 1. Human Error Mishaps Statistics from 1 Jan 86 – 31 Dec 90C: UsersJohnathanDocumentsResearch.jpg


When looking at any composite system, it is easy to see that jobs and failures in the system are straight linked with human mistakes. These include specifications that are n’t completed, issues with the design of the system and package misreckonings and technology defects. But when we are concentrating on human mistakes in an deep-rooted system, we see issues caused by a hapless Human Computer Interface.

What is Human Computer Interface?

Is the survey of the relationships which exist between human operators and the Computer systems they use in the public presentation of their assorted undertakings.

We as worlds have inclination to do errors and certain conditions can merely increase the opportunities of doing more and more errors. When a well-designed and thought out HCI ( Human Computer Interface ) is created, a user is more prone to come in right values and non to do easy errors on the system, due to the fact that they understand what is asked from them. Unfortunately there is no distinguishable manner to make a HCI for systems.

Embedded systems normally have a fixed cost and control and ca n’t make highly complex computations. Therefore an interface has to designed so that it will be simple and easy to utilize without utilizing excessively much of the systems so that it will still be safe. We have to distinguish between extremely field specific interfaces ( Nuclear Power Plants ) and easy entree interfaces like Automatic Teller Machines or onscreen bill of fares like a cell phone. The easiest manner to understand what is meant with this is if you look at any common vehicle.

Everyone has to travel for a driver ‘s trial to be able to drive a auto, but the inside of modern twenty-four hours autos differ and this causes a driver ( user ) to do a error when seeking to drive the auto because they are unfamiliar with it. This is where human mistake comes in to play.

The chief issue to command in a safety critical system is to forestall the human user signifier doing an mistake that causes hazard. Usability is a immense factor when making a HCI. This is because if the serviceability is easy to understand the user will be more relaxed and have reduced jitteriness. But by doing the HCI to easy and simple, an operator can misjudge an mistake and take to go on with the mistake that can make tremendous mistakes. Such an mistake occurred with the THERAC-25 medical radiation device. The operator would merely choose dose and non read what was being displayed on the interface and he so administered deadly doses of radiation to the clients. Mistake messages are besides an of import portion in HCI. A if message should happen it should be in such a mode that the interface is fundamentally stops to demo the mistake and the operator should disregard the message by admiting that he/she has read the message so that the message can answer with feedback if it has succeeded or failed.

Cardinal Theories

In an embedded system a Human user is normally the frailest nexus. The opportunities of a human operator to make a error in a computing machine system are higher than the existent constituents and or package to neglect. The technique used to find the chance that a human will make an mistake throughout the completion of the undertaking is called the Human Error Assessment and Reduction Technique ( H.E.A.R.T ) . The grounds to utilize the HEART method are for the followers:

Mistake Designation

Mistake Quantification

Mistake Decrease

HEART method is grounded upon the belief that every clip a undertaking is performed there is a possibility of failure and that theA probabilityA of this is affected by one or more Mistakes Producing Conditions ( EPCs ) – for case: distraction, fatigue, cramped conditions etc.

HEART Method


Entire HEART Effect

Assessed Proportion of Effect

Assessed Consequence




( 3.0-1 ) x 0.4 + 1 =1.8

Opposite technique



( 6.0-1 ) x 1.0 + 1 =6.0

Hazard Misperception



( 4.0-1 ) x 0.8 + 1 =3.4

Conflict of Aims



( 2.5-1 ) x 0.8 + 1 =2.2

Low Morale



( 1.2-1 ) x 0.6 + 1 =1.12

Table 1. Computational factors in ciphering the Human Error Assessment and Reduction Technique.

A representation of this state of affairs utilizing the HEART methodological analysis would be done as follows:

From the relevant tabular arraies it can be established that the type of undertaking in this state of affairs is of the type ( F ) which is defined as ‘Restore or switch a system to original or new province followers processs, with some look intoing ‘ . This undertaking type has the proposed nominal human undependability value of 0.003.

The concluding computation for the normal likeliness of failure can hence be formulated as:

0.003 ten 1.8 ten 6.0 ten 3.4 ten 2.2 ten 1.12 = 0.27

Foundations of Human Error

Systems working on Auto are really good at making insistent undertakings. But if by opportunity something happens to the system and counteractive actions must be taken, this is when the system reacts out of order. This is when a Human is needed to manage the crisis. Worlds are better at managing new types of incidences than the machines themselves, but the worlds can non execute humdrum undertakings as good. Consequently the Humans are left in charge of supervising the system inactively. This creates a job because if the operator is n’t busy with work the whole clip they become world-weary and therefore overlook greater mistakes that can happen. This is called Operator Drop-Out.

Though, if the operator is invariably busy with everyday work by commanding the system, he/ she will besides do errors, because they become used to the same thing over and over and the minute that there is demand for attending they wo n’t be able to respond to it as a NEW job. If the operator has a determined mental ideal of the system in its normal manner of operation, the operator will tend to disregard informations stand foring an mistake unless it is displayed with a high degree of differentiation.

Another major factor act uponing the operator is: Stress. Straitening fortunes include:

Unfamiliar happenings

Incidents that can do money, information, life loss

Time critical undertakings

We as worlds tend to degrade our public presentation when we are threatened with nerve-racking state of affairss. The best manner to cut down this consequence is to do unusual state of affairss accustomed by utilizing drills. The minutes when worlds are expected to execute at their best is when the highest degrees of emphasis occur doing them more prone to do mistakes on the system. Failure rate in some state of affairss can lift to every bit much as 30 % . Unfortunately, worlds are our lone pick, since a computing machine system can non rectify itself in complex state of affairss or crises. The best that can be done is to plan the user interface easy to understand and utilize so that the user will do less errors that can do more harm.

Understanding Human Mistakes

The Action Theory and Human Mistakes

In 1978 Leontief developed a manner to seek and understand how human mistake occurs. It is called the Leontief ‘s Three – Degree Schema ( See Figure 1 ) . It defines the range of question of human activities and guides the attending to the alterations go oning on these three degrees: motivation activity, end action, and instrumental conditions-operations. These three degrees are ordered in a tiered agreement where the top degree of activities includes legion actions that are performed by right operations. In a ‘pure ‘ indifferent manner merely the active degree can be observed and analysed. The end scene and motivational degree must be attendant or examined by indirect methods ( e.g. , questionnaire, interview, believing aloud, etc. ) based on the brooding comments of the examined topics.

hypertext transfer protocol: // ( diagram ) 1.jpg

Figure 2. The three degrees scheme of the activity theory of ( Leontief, 1978 ) .

Solving or Minimizing Human Mistake

The undermentioned features lead to human mistake and we need to name these to work out it:

Low Stress Mistake

High Stress Error

Error/Change Phenomena

Low Stress Mistake

Have you of all time walked into a room to make something but merely as you enter the room you have forgotten what you wanted to make? This is a authoritative illustration of a Low Stress Error. An enterprise non carried out holding to the program. These cockamamie things happen to us because we are human. But these types of human mistakes in processing and of import state of affairss can get down some grave concerns.

For illustration, we have a control box with a sequence of start and halt switches about 13mm apart. These buttons control legion operational pumps. When the incorrect switch is activated or deactivated at a critical minute in clip, it is an action that was carried out non harmonizing to the particulars needed to run the machine. This can make immense jobs because the pipes that need to chill down are now working once more and approaching detonation.

A simple and easy manner to work out this type of job is through increasing the infinites between each button and switch or even labelling them with text or neckbands. In other words the User Interface will alter so that it wo n’t let a simple human mistake to happen.

High Stress Error

The twenty-four hours that the Three Mile Island accident occurred, over a 100 dismaies and whistlings went off and the human operators that were working with the nuclear-powered machineries did the incorrect things in the clip of demand. In all the terror and noise they really shut off the chief chilling system that was the most of import thing that was needed in the exigency. This type of high emphasis mistake is non uncommon. Harmonizing to a survey on the mistake potency of people who all of a sudden are faced with at hand danger, if they have merely one minute to respond to an out-of-control state of affairs there is a 99.9 % opportunity of making the incorrect thing. There is a 90 % opportunity if they have five proceedingss to respond, 10 % with a half hr to respond, and 1 % ( still excessively much ) with 2 hours to respond.

This mistake can be minimized though the followers:

Hazard hazard analysis for progress warning of possible jeopardies.

Automated designs for short clip intervals for determination devising that are excessively rapid for worlds to respond.

Design of clear information shows and systems that do non confound and disorient people when disquieted fortunes occur.

Practice preparation in how to get by with system disturbances.

Error/Change Phenomena

It must besides be said that a calamity about ne’er occurs with merely one human mistake. Human mistake is portion of being human and we are surrounded by it. Every mistake we get alterations our environment. It may happen as a reactor that is vibrating out of topographic point when it is making something incorrect. Scientists tell us that it takes about 14 of these misreckoning constituents of a concatenation to present us with a bona fide calamity. The ground we survive this overpowering prospective is because we are repeatedly seeing these alterations and taking action to interruption the restraints.

Problems with the HCI

It is expected of the HCI to present natural controls and the right advice to the user. An issue with the HCI is normally that is causes information overload. When it is expected of the human to concentrate on several screens to detect the position of the machine, he/she can acquire overwhelmed doing them unable to react to the informations or mistakes on the system. This causes the operator to disregard shows that are holding little sums of information content displaying at that minute. This is hazarders if that specific show is in charge of an of import detector. A different manner to steep an operator is by seting a notifying dismay on every action he does. This renders him/her incapable of cognizing when it is a existent menace or merely a minor mistake. Much like the “ Cry Wolf ” narrative

HCI should besides hold a high assurance degree that will allow a homo operator to measure the information it is exposing and to verify and formalize it without any issues. The homo should non hold to depend on the show of the system for devices. The HCI should besides non expose more than one detector per show. This can do confusion and errors to go on. Worlds should besides non confide in the grounds from the HCI to the skip of the remainder of his/her milieus.

There are a few job work outing techniques for interceding a well-designed user interface, but there is no methodical method for planing safe, useable HCI ‘s. It is besides debatable to quantitatively mensurate the safety and serviceability of an interface, every bit good as discovery and correct for defects.

Available tools, techniques, and prosodies for HCI

There are a few techniques for making user interface designs, but they are non yet to the full developed and they ca n’t offer decisive informations about a HCI ‘s safety and serviceability. Review approaches like heuristic appraisal and cognitive walkthroughs have the advantage that they can be applied at the scheme phase. Another debatable case, is the issue that a existent interface is n’t being verified, besides limits what can really be determined by the HCI design. Experiential processs like protocol analysis basically have existent users that test the user interface, and do extended surveies on all the informations collected during the session, from key strokes to sneak chinks to the user ‘s verbal history during interaction.

The Design of a HCI

There are no existent processs for a user interface design. However there are a few regulations and abilities that are of import for a functional safe HCI, but the exact manner of achieving these qualities are non good understood. The safest and best process to follow is the iterative design, rating and redesign. If we can execute efficient ratings and right place as many defects as possible, the interface will be greatly improved. Correct appraisals antecedently in the design stage can salvage money and time.A It is easier to happen HCI defects when you have an existent interface to work with.A It is besides critical to separate design of the HCI from other mechanisms in the system, so defects in the interface do non dispersed mistakes through the system.

Degree centigrades: UsersJohnathanDocumentsResearch2.gif

Figure 3. Development procedure of a HCI

Iterative User Interface Design

Iterative betterment of user interfaces encompasses stable alteration of the design grounded on user testing and other appraisal agencies. Normally, one would finish a design and log the jobs several trial users had utilizing it. These bugs would so be fixed in a new reduplication which should once more be tested to guarantee that the “ holes ” were genuinely solved and to happen any new serviceability complications presented by the transformed design. The design deviates from one loop to the ensuing one and those are usually local to those exact interface basicss that caused user complications. An iterative design methodological analysis does non affect unseeingly replacing interface elements with different new design thoughts. If one has to choose between two or more interface options, it is likely to execute comparative proving to amount which option is the most practical, but such trials are normally viewed as making a different methodological analysis than iterative design as such, and they may be performed with a focal point on in depth alternatively of the result of serviceability jobs. Iterative design is explicitly intended at alteration based on lessons learned from old loops.

Name of the system

Interface Technology




per trial

Overall Improvement



Personal – Computer graphical interface



242 %

Cash Register

Specialized hardware with character based interface



87 %


Mainframe character-based interface



882 %


Workstation graphical user interface



41 %

Table 2. Four instance surveies of iterative design.

Degree centigrades: UsersJohnathanDocumentsiterative_design_improvements.gif

Figure 4. Interface quality as a map of the figure of design loops: Measured serviceability will usually travel up for each extra loop, until the design potentially reaches a point where it plateaus.

What Is Heuristic Evaluation?

This is when a group of people ( examiners ) evaluate a user interface design and criticise it based on a set of “ easiness of usage ” guidelines. These guidelines or stairss can non be concretely measured, but the testicles can do comparative opinion about how good the user interface adheres to the guidelines or stairss.

The followers are a few of these guidelines or stairss:

Simple and natural duologue

Talk the users ‘ linguistic communication

Minimize the users ‘ memory burden



Clearly marked issues


Precise and constructive mistake messages

Prevent mistakes

Aid and certification

These guidelines are implemented early in the life rhythm of a system, since the examiners wo n’t be working on an existent interface. Each examiner will inspect and measure the interface, knocking it on the set of guidelines. This process is merely an rating method that validates your interface harmonizing to the antecedently mentioned guidelines. To make optimum coverage of all the possible countries of the User Interface, a little squad of 5 examiners will be needed to finish the undertaking. The ruin with this method is that it is really dearly-won and at most merely 3 examiners are normally hired or brought in to measure a user interface.

This method of user interface design is exceptionally good at observing errors and lucubrating on why there are usability jobs on the interface. Once the examiners have uncovered the cause of unstable serviceability, it is easy to develop a solution for that job to repair it. Fortunately it can salvage you a batch of clip and prevent mistakes, because the issues have been uncovered before it has really started impacting the user interface. The disadvantage of this method is that all the good qualities of this method are dependent on the accomplishments of the examiners that are proving you user interface. Adept examiners that are qualified in the field of the system can acknowledge interface jobs for that exact field in a system.

What are Cognitive walkthroughs?

This method like the old method can be tested on the design of the HCI without the demand of really building it. Nevertheless the rational walkthrough tests the system by concentrating on how an abstract operator of the Interface goes about executing a undertaking. Every measure the operator takes is examined and evaluated and so criticised on how good the user understood what the interface wanted from him/her. The HCI should ever supply a suited sum of advice to corroborate that the operator is doing advancement on his/her undertaking.

By doing usage of the rational walkthrough method it can bring out the differences in how the users and the interior decorators view these undertakings that they have to finish. It besides reveals hapless cataloguing and deficient feedback for certain actions. But this method besides misses a few of import serviceability facets due to the fact that it has a tight focal point on other parts of the user interface. The cognitive walkthrough method can non prove the cosmopolitan dependableness or deepness of characteristics. It can besides knock a user interface to be ill designed because it gives the operator excessively many picks to take from.

For a user interface to be well-designed it has to hold every bit few as possible mistakes and review methods needed to measure the user interface. There are via medias between how carefully the interface is looked at and how many belongingss are able to be dedicated at this early phase in the system life rhythm. Experimental processs can besides be applied at the sample measure to really observe the public presentation of the user interface in action.

Define Protocol Analysis:

This is an experimental process of user interface proving that concentrates on the operator ‘s vocal replies. The operator is instructed to utilize the interface and is asked to “ believe out loud ” when working through the stairss of executing his/her undertaking utilizing the system. Ocular and Audio information are logged, including the mouse chinks and key strokes on the keyboard or cardinal tablets used to entree the system. By analyzing each piece of informations received throughout this trial, is a really clip devouring undertaking, since we have to make premises from the single vocal replies of the operator and make readings from his/her facial linguistic communications. This undertaking is tiring merely because the entire sum of information is really high and drawn-out surveies are required for each second.


This is a tool that was developed at the Carnegie Mellon University to automatically run the undertakings of a normal deadening undertaking of assemblage and analyzing all the information that was accumulated from experimental user interface trials. This system is made up of package that synchronizes the method of information from a few available resources when an operator is utilizing the interface being tested. All possible inputs from the operator like the key strokes, chinks of the mouse even the oculus motion and the vocals of the operator are logged for processing. This procedure is based on that if the interface has a good serviceability property, the operator will non hesitate during the current session, but will go on from one measure to the other as he/she finishes the undertakings that was assigned to them. Any unusual intermissions between activities would be shown as mistakes on the system and the job can be detected automatically and truly fast.

This tool gives us more quantitative consequences and diminish the clip spent roll uping and treating informations from each trial station. The lone disadvantage that this method has is an mistake that causes the operator to hover in a undertaking.

Other subjects related to HCI

Because human mistake is the major cause of system failures, it must be a big influence in safety critical system analysis.

Safety Critical Systems/AnalysisA – Human mistake is a chief issue that is doing systems safety life-threatening.A It is debatable to pattern human behavior in a system analysis, but the human operator is frequently a major failing to doing a system safe.

Exception HandlingA – The human operator is frequently a beginning of superb attempts to the system.A But, when a genuinely surprising province occurs, the human operator is the lone exclusion animal trainer and the lone tool able to forestall system failure.

SecurityA – Defects in the user interface can sometimes be broken and present safety exposures to the system.

Social and Legal ConcernsA – If the user interface was ill designed and caused the operator to do a error that cost lives or belongings, who is at mistake? A The operator? A The system interior decorator? These issues must be addressed by society and the legal system.


Worlds are the most fickle fragment of any system and so the most ambitious to hone for HCI design.

Worlds have greater failure sums under high emphasis degrees, but are flexible in bettering from exigency fortunes and the last hope in a possible calamity.

The HCI must supply an suited degree of response without overburdening the operator with excessively much stuff

If the homo operator is out of the control cringle in a computerized undertaking, the operator will be given to accommodate to the standard procedure manner and non pay close devotedness to the system. When an exigency status occurs, the operator ‘s response will be degraded.

There is a difference between doing the HCI reasonably easy and self-generated and guaranting that system safety is non negotiated by tiring the operator into a province of complacency.

Testing methods for user interfaces are non developed and can be costly.A They focus more of qualitative instead than mensurable metrics.A However, proving and insistent design is the best manner we have for polishing the interface.

Worlds will do errors it is inevitable. But by working about operators we can analyse how they think and therefore make a User Interface that will be easy to understand and unique to each.

Research Methodologies Used

Historical Research:

I gathered information from assorted web sites refering the yesteryear of Human Computer Interfaces and how it changed.


I conducted an interview with Professor Paula Kotze, who is a close household friend. She gave me some arrows on how to make research on my subject and she besides gave me a few articles ( in my mention ) that were really utile in my development of my research subject.

Experimental Research:

I gathered information on old instance surveies for HCI and implemented it into my undertaking.

Action Research:

I decided on a subject and so I did research on jobs within my topic country.

List of Figures and Tables

Figure 1. Human Error Mishaps Statistics from 1 Jan 86 – 31 Dec 90 aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦.3

Figure 2. The three degrees scheme of the activity theory of ( Leontief, 1978 ) aˆ¦aˆ¦aˆ¦.7

Figure 3. Development procedure of a HCIaˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦..aˆ¦11

Figure 4. Interface quality as a map of the figure of design loops: Measured serviceability will usually travel up for each extra loop, until the design potentially reaches a point where it plateausaˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦ … 12

Table 1. Computational factors in ciphering the Human Error Assessment and Reduction Techniqueaˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦..5

Table 2. Four instance surveies of iterative designaˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦aˆ¦12

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