An Analysis of Domestic Cooker Control Design

8/11/2019 An Analysis of Domestic Cooker Control Design

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An analysis of domestic cooker control designR.D. RAY a & W.D. RAY ba Robert Gordon's Institute of Technology , Aberdeenb Birkbeck College, University of LondonPublished online: 24 Oct 2007.

To cite this article: R.D. RAY & W.D. RAY (1979) An analysis of domestic cooker control design, Ergonomics, 22:11, 1243-1248

To link to this article: http://dx.doi.org/10.1080/00140137908924698

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ERGONOMICS, 1979, VOL. 22, NO II 1243-1248

An analysis of domestic cooker control design

By R. D YRobert Gordon s institute of Technology, Aberdeen

an d W. D. YBirkbeck College, University of London

This study isan attempt to identify, the particular arrangement of the controls of a domesticcooker which w ould be the most n at ural and efficient to usc. A coo ke r h ob s im ul at orcapable of providing bo th in line n d in quadrature r ing layouts, and different ringcontrol arrangements was used. Twenty-eight students car ried out t rial s on the s imulatorand their error rates were measured. A new sta ti st ical test was used to show tha t on e of thering-control arrangements for the in quadrature rings, gave significantly less errors than theother three and hence could be regarded as the eas iest to use.

IntroductionTh e efficiency and ease of use of most machines and equipment depends on a

variety of factors ; on e of these is fairly clearly the layout an d operation of the controls.In the home, on e of the most complicated array of controls to be seen iso n the moderncooker whether gas or e lec tric , wh ere o ft en six or more cont ro l knobs on taps arearranged on the front or re ar panels. As a general rule these controls are placed inl ine on e for the o ven, on e for the gri ll , an d fou r for the ho b rings or burners. Th eoven and grill controls which ar e probably used less frequently are usually placed ateither end of the array or together in the centre an d do no t normally present a realproblem of identification or operation. The arrangement of the four ho b ring controlshowever may vary appreciably, an d being more frequently used often cause problemsof identification an d error an d are the subject of this article.

2. BackgroundT he mos t common form of design in manufacture seems to be to have the controls

. in line operating the ho b rings arranged in quadrature. With this spatial arrange-ment it is c lear that four different designs of ho b rings an d their c on tr ol s a re p rob -able as shown in Figure 1. In fact all four of these arrangements have been manu-faciured. The fact that the controls an d the rings have different configurat ions oftenpresents the difficulty of relat ing a given control with its ho b ring. If the controlarray is symmetrical with the ring configurat ion, then it is fairly obvious that the tworight h an d k no bs are associa ted with the two right hand rings, and similarly for theleft hand side. It isless clear howeverwhich of an y two controls is related to a particularring. It could be argued of course that the controls would be identified with words orsymbols, and would therefore present no difficulty in usage. Even with some form ofidentificat ion, it is probable that the user will operate the controls automaticallyaccording to some plan established on another or earlier model.

Th e variat ion in performance of people operat ing controls lead Fitts and Seeger 1953) to suggest the idea o f compatability of displays i e rings) with the ir controls. This inferred that there may be certa in natural lin kages with in a p erson sthought processes which connected some display with its control. Welford 1968) alsomentioned the possibility that people may form men ta l mod el s by which they ar e

0 0 l ~ I J 1 N J 7 9 / 2 : 1 11243 02.00 d 1979 Taylor Francis Ltd


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An analvsis domestic cooker control design 1245

The quest ion is then, is there a s ingle arrangement which could be regarded as them os t n at ur al design which would lead to eas ie r operation an d fewer errors i e ist he re a populat ion stereotype? If such a stereotype existed, it should be possible to

recommend that arrangement as a standard. In fact in an edition of the ConsumersAssociation magazine Which 1977 following several tests both here and inAmerica, arrangement A4 was recommended as the best.

3. MethodIn order to gain an im press ion o f th e frequency of the four designs in exist ing

cookers, a brief survey o f those in the kitchens of this Insti tute showed that all fourarrangements were evident. These were naturally no t new designs bu t varied in age.Th e 35 cookers examined are classified in Table I

Table I.

AI

9

A2

5

5

A4

16

A review o f new gas cookers at present on the market showed that of th e 14different models examined, 6 were of arrangement A I, an d 8 were of arrangement A4,bu t none of arrangements A2 an d A3. In th e case of electric models, all the cookersobserved were f rom four main manufac turers an d these appeared to divide equally,two employing arrangement A I an d two arrangement A4.

In th e experiment, following Chapanis an d Lindenbaum 1953 , a cooker ho bwas simulated using coloured perspex discs to represent th e rings, each of whichcould be illuminated by bulbs opera ted from a swi tching panel . Th e circuits werearranged so that anyone of the rings could be s witched on at the p anel an d of f by thesubject using the correct control knob. Th e c on tr ol knobs were fitted on the frontpanel of t he h ob with an i n line configuration bu t wit hou t a ny identification.Also, by adjus ting the wiring, all th e ho b ring an d contro l ar rangements could be

constructed without physically altering the knobs.Twenty-eight female subjects, all students took part an d in th e first instancewere asked to record th e arrangement which they preferred best. Each subject waspresented with a series of ring s ignals in a random manner first with the r ings in lineas Figure 2 an d then with th e quadrature arrangements; the presentation o f the lat terwas a lso randomized. Th e s ignals were given in fairly quick succession bu t withslight variat ions in t ime between each signal to avoid anticipation. Th e subject wasinstructed to switch off th e r ing l ight as quickly as possib le , with what they thoughtwas the correct control. Each subject carried ou t 20 trials o n each arrangement an dtheir errors, i e operat ing the wrong control were noted for each test.

4. Analysis of Results4 Preferred Arranqements

As the experiment was concerned with quadrature designs only, from the point ofview of preference, the r ings in l ine arrangement was no t considered here. Th esubjects recorded th e preferences, shown in Table 2.

Table 2.

AI

6

A2

7

5

A4

1


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46 R. D. Rayand W. D. Ray

4.2. Hob Rinqs LineIt was found that with the rings in line , no subject incurred any error s b ot h with

the cont rol knobs extended an d in the closed in pos it ion.

4.3. Hob Rinqs /11 QuadratureThe results of the experiments on the four in quadrature arrangements expressed

in terms of subject errors are given in Table 3. It is pres ume d tha t the most efficientor easily operated design wou ld be that involving the least number of errors: th eanalysis thus involves th e statistical question of selection.

Table 3. Experimental Results

AI A2 A3 A

umber of Trials 560 560 560 560 umber rrors 6 ~ 91 107 48 ercentage of rrors 12 2 163 19 2 86

umber

Successes 492 469 453 512Proportion of Successes ~ 7 9 0838 0809 0-914

None of the class ical s ta ti st ical tes ts a ns we r t he question of which of severalpopulations isthe best in some characteristic. It isonly fairly recently that appropriatestatist ical tests have been devised a nd bec om e available. is therefore proposed tofo llow the recent work of Gibbons, Olkin, an d Sobel 1977) who do in fact lamentt ha t s uch exis ting t heory has no t been used more extensively on applied problemsof this kind.

In order to be able to make some valid probabil ity statements from the s am pl einformation. certa in t erms need to be defined. Let be the number of trials carriedou t on each control arrangement. It is then necessary to define a distance measure 0,which is the difference beteen th e largest an d second largest probabili ty of successamong the k binomial populations of th e experiment. Thus we ma y write,

= Plk] Plk-I I

T he n umb er of populations is four in this exper iment.We must then specify a value of 0 = 0* E 0 , I) which gives an indifference zone

within which we would no t wish to discriminate the largest p, an d a preference zonewhere we would. We finally define P, to be the probabi li ty of making a correctselection of the largest p value.

If P = PI P2 Pk then P = p CSlp) is the probability of correct selection CS), whatever th e values of P in the preference zone. This is e ither very difficult orimpossible to determine. However there may be a cer ta in point or region P in thepreference zone whose P = P CS\Pu-) = P*, is the minimum of P over all p. This

configurationP

is called the least favourable configuration an d we may wri teP CSlp) ;;, P CSIPLF)

for all P in the preference zone. is important to no te that solving P in this way,given an d 0* _gives a conservative answer. Thus we ca n be certain that the probabilityof correct selection is at least P*, a nd ma y be a lot g reate r.

It is apparent that control arrangement A4 has the best performance based on theexperimental information obta ined, but with what confidence ca n this be claimed?


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An analysis domestic cooker control design 1247

The procedure is first to specify a value of


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48 R. D. Ray and W. D. Ray

ReferencesCHAPANIS A. an d LINDENBAUM E. 1953 A reaction time study o f four control-display linkages.

Human Factors 1 1 7.GI ONS J. D OLK N I. and SOBEL M 1977 Selection and Ordering 0/ Populations A New Statistical

Methodology . Ne w York: J. WILEY SONS .FITTS P. M. an d SEEGER C. M. 1953 S- R compatibility: spatia l characteristics of stimulus an d response

codes. Journal Experimental Psychology 46 199-210.WELFORD A. T. 1968 Fundamentals Skill. London: METHUEN .Which? Sept. 1977 Consumers Association.

Manuscript received 20 February 1979Revised manuscript received 30 April 1979.

An Analysis of Domestic Cooker Control Design

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