USING A MODIFIED MOUSE TO READ DATA FROM NONSTRUCTURED LINE SCALES

RICARDO SANCHEZ and GUILLERMO HOUGH's2

Instituto Superior Experimental de Tecnologia Alimentaria 6500 Nueve de Julio

Buenos Aires, Argentina

Received for Publication January 16, 1996

ABSTRACT

Nonstructured line scales (NLS) are widely used in sensory and consumer research, normally generating a large amount of data to be introduced to com- puters for statistical analysis. This process can be very much accelerated with the use of special hardware and somare. Available systems are eficient but costly. To overcome this last item a standard mouse was modified to be used as a measur- ing instrument, and a simple QBASIC program was developed to input the measured data into an ASCII$le. The cost of the modified mouse was $60, and data input was 5 times faster than measuring distances with a ruler. Experiments designed to test the mouse showed that error measurements were small.

INTRODUCTION

Nonstructured line scales (NLS) are widely used in sensory and consumer research, normally generating a large amount of data to be introduced to com- puters for statistical analysis. A standard descriptive analysis of 3 samples, cover- ing 20 descriptors and performed by 10 assessors, means 600 values to be read. Traditionally these values were measured with a ruler and then typed into a com- puter. This system is time consuming and can lead to mistakes. In the last years a number of systems have been published which automate

data entry. McLellan and Cash (1983) developed a program for each assessor

'Research fellow of the Comisi6n de Investigaciones Cientificas de la Provincia de Buenos Aires. Torresponding author: Guillermo Hough, ISETA, 6500 Nueve de Julio, Buenos Aires, Argentina. FAX: (54) (317) 22305.

Journal of Sensory Studies 12 (1997) 1-9. Alf Rights Reserved. 0 Copyright 1997 by Food C? Nutrition Press, Inc., Trumbull, Connecticut. 1

2 R. SANCHEZ and G . HOUGH

to enter his data through a terminal using the keyboard. Brady et al. ( 1 985) used an inexpensive data collection unit for each assessor. with all units connected to a central computer. The drawback of this system was having to use specially made forms to fit over the units. McLellan et af. (1987) used a scanner to read values from custom designed forms. This system is relatively inexpensive, but requires previously printed forms which reduces flexibility in designing an ex- periment. Grid pads which are operated by assessors with an optical pen, and which emulate the traditional paper and pencil forms have also been used (Billmeyer and Wyman 1991; Thompson and Malek 1993).

Having a computer terminal in each cubicle is expensive in hardware: for 10 assessor stations, approximately $13,OOO. These systems require specialized soft- ware which vary in price from approximately $20,000 to $40,000 (Biosystemes, Couternon, France; Oliemans Punter en Partners, Utrecht, Netherlands; Sensory Computer Systems, East Hanover, New Jersey).

The objective of the present work was automating data entry from NLS using a low-cost modified mouse with simple software; and comparing its performance to traditional manual ruler measurement.

MATERIALS

Hardware

A standard three key mouse (Leadgen Model LE260, Taiwan) connected to an IBM compatible PC was used. A mouse is an accessory not originally designed to measure distances. It uses a steel sphere covered with a rubber-like polymer connected to two axles which account for horizontal and vertical movements. Each of these axles are in contact with sprockets whose teeth interrupt a beam of light as shown in Fig. 1 . The interruption of the beam of light is picked up by the computer as a signal which converts it to a screen position.

For the purpose of measuring distances from NLS we were only interested in the horizontal movement of the mouse, thus we eliminated the axle and sprocket which registered vertical movements. For the horizontal movement to be more precise the mouse’s sphere was replaced with a 40-teeth sprocket which moved over a 15 cm rack as shown in Fig. 2 . The 40-teeth sprocket was in contact with a smaller 10-teeth sprocket fitted over the axle of the mouse’s horizontal move- ment sprocket, also shown in Fig. 2. The rack was made by filling a crevice in the acrylic base which a plastic cement (Poxilina, Akapol Inc., Buenos A i m , Argentina) and running the 40-teeth sprocket over it before it dried to mark the little holes.

Figure 3 shows the following: ( I ) The rack clamped to the computer table; ( 2 ) a needle attached to the mouse to point to the assessor’s mark on the score

USING A MOUSE 3

FIG. 1. MOUSE BEFORE MODIFICATION

FIG. 2. MODIFIED MOUSE WITH SPROCKET TO REGISTER HORIZONTAL MOVEMENT OVER A 15-CM RACK

4 R. SANCHEZ and G . HOUGH

FIG. 3 . MODIFIED MOUSE FITTED OVER A RACK AND WITH AN ATTACHED NEEDLE TO POINT TO MARKS ON NONSTRUCTURED LINEAR SCALES

sheet, and (3) also clamped to the table a guide for the needle and score sheet. A local watchmaker provided the sprockets and helped with the modifications.

The total cost of the modified mouse was approximately $60. When using the modified mouse to measure distances two caveats should be

considered: (1) Abrupt or very fast movements of the mouse produce errors in the measurements, and (2) Every time a new page of scales is to be measured, the needle of the mouse should be placed 5 mm to the left of the scale’s nil value.

Software

QBASIC (Microsoft Corporation, Redmond, Washington) was used to create an ASCII file from the mouse readings. Figure 4 shows a portion of a descriptive analysis with scales marked by the assessor. Table 1 is the QBASIC program used to create the file from the mouse readings of Fig. 4, and Table 2 shows the ASCII file in a format to be read by statistical software such as Genstat (1993). The program can be modified according to the structure of the score sheets used in each experiment.

5 USING A MOUSE

D E S C R I P T I V E ANALYSIS O F CHOCOLATE MILK

NAME: . . . . . . . . . . . . . . . . . . . . . . DATE: . . . . / . . . . I . . . .

I COLOR INTENSITY

very light very dark

Sample 602

Sample 244

RED COLOR no red very red

Sample 437

Sample 602

Sample 244

(Etcetera)

FIG. 4. PORTION OF SCORE SHEET TO BE READ USING THE MODIFIED MOUSE AND THE QBASIC PROGRAM OF TABLE 1

TESTING OF THE MOUSE

Experiment 1

This first experiment was conducted to compare the performances of the ruler and the mouse measurements as regards time and repeatability. For this purpose a score sheet was made up simulating an analysis of 3 samples using 14 descrip- tors, distributed over 2 pages. On each page, 3 of the 21 NLS were randomly selected to be marked with fixed distances: 13,50 and 95 mm on 100 mm scales. The rest of the NLS were marked with random distances. This process was repeated for 6 score sheets, simulating 6 assessors. The 6 score sheets were then measured using a ruler and the mouse.

With this design, 12 measurement repetitions were obtained for each distance, without the person involved in the measurement being aware of these repetitions. Neither was she aware that her time performance was being registered.

6 R. SANCHEZ and G. HOUGH

TABLE 1 . QBASIC PROGRAM USED TO ENTER DATA TO AN ASCII FILE FROM MOUSE READINGS

OF SCORE SHEETS LIKE SHOWN IN FIG. 4

REM REM Enters session VariablOS REM INPUT "Number of assessors";NASSESS INPUT "Number of descript0rs";NDES INPUT "Number of samp1es";NSAM REM REM Defines the size of indexed variables and REM enters the names of sensory descriptors REM DIM X(NASSESS,NDES,NSAM) ,DESS(NDES) ,SAMPNUM(NASSESS.NSAM) PRINT:PRINT '"Please enter the names of descriptors" FOR J-1 TO NDES PRINT "Descriptor "J" : " ; :INPUT DESS (J) NEXT J REM ReM 0p.n. th8 1ss.sSor loop and allows for REM different order of sample preaantation REM FOR K-1 TO NASSESS

CLS PRINT '"Prepare the score sheet for" PRINT "assessor "K:PRINT FOR ORDER=l TO NSAM

PRINT "Number of sample in order -"ORDER; INPUT SAMPNUM(K,ORDER)

NEXT 0RDER:PRINT REM REM opens the descriptor and sample loops and REM raceivas data fror the mousa REM FOR J=l TO NDES

PRINT " Descriptor * ; D E S S ( J ) FOR I=1 TO NSAM

100 P-PEN()) I F P THEN X(K.J.1)- PEN(41 E L S E 100 XIK,J,I)- X(K,J,I)*100/46 PRINT "X=";X(K,J, I1 DO W I L E P PI PEN(3) LOOP

NEXT I NEXT J

NEXT K REM REM Creates an ASCII f i l e from data read with the mouse R EM

FOR K-1 TO NASSESS OPEN *C:\DESCRIP.DAT" FOR OUTPUT AS n l

FOR I=1 TO NSAM PRINT U 1 . K ; I; SAMPNUMIK.1); FOR J-1 TO NDES

NEXT J PRINT U 1

PRINT #l.X(K,J.I):

NEXT I NEXT K CLOSE $41 END

USING A MOUSE 7

TABLE 2 . PORTION OF AN ASCII FILE CREATED BY THE QBASJC PROGRAM (TABLE 1) FROM

READINGS TAKEN BY THE MOUSE FROM A DESCRIPTIVE ANALYSIS

ASSESSOR ORDER SAMPLE COLOR RED SPOTS 1 1 437 45 1 2 2 1 1 2 602 5 6 1 5 5 1 3 244 23 6 4 7 2 1 602 67 2 3 1 2 2 2 2 4 4 3 5 4 77 2 3 4 3 7 58 11 32

Experiment 2

This second experiment was performed to compare measurement errors (registered in Experiment 1) with assessor variations in marking NLS. Line lengths were used as stimulus and were measured visually. Length is easily understood and is linearly related with its sensory evaluation (Moskowitz 1977). Assessors had a page stuck up in front of them as shown in Fig. 5a. The ‘very long’ reference was 100 mm long, and the lines to be evaluated were 13, 50 and 95 mm long; the same lengths as the marks of Experiment 1 . The score sheet they used is in Fig. 5b, of which they received twelve repetitions in one session. For each repeti- tion the sample codes were presented in random order. The completed score sheet was withdrawn before presenting a new one. A total of 10 assessors performed these visual evaluations.

With assessors knowing each measurement was a repetition of the previous one, and linear length being easily evaluated, the major source of variation from one repetition to another was the actual mark on the NLS.

RESULTS

From Experiment 1 the following reuslts were obtained: (1) Measuring the 252 scales with a ruler and writing the measured distance

next to each scale took 30 min. To enter the data to an ASCII file from the keyboard took another 27 min. With the mouse it took 12 min to have the ASCII file ready, i.e., only a 21% of the time it took with a ruler.

(2) Distances measured with the ruler and mouse were almost identical and corresponded to the actual distances marked on the scales (see Table 3).

(3) On one of the randomly marked scales, when using the ruler, the person should have written the distance as “91 ” and instead she wrote “19”. This

8 R. SANCHEZ and G. HOUGH

(a)

REFERENCES FOR VISUAL LENGTH MEASUREMENTS

VERY SHORT

VERY LONG

LINES TO BE EVALUATED

Line N o 802

Line N" 682 - Line N o 336

(b) Please observe the page in front of you and, guided by the references, make a visual evaluation of the length of the numbered lines by making a mark on the corresponding scale. Make your evaluations in the order of this score sheet. Thank you.

very short very long

Line N o 336

Line N o 802

Line N" 682

FIG. 5. (a) LENGTH REFERENCES (0 AND 100 MM) AND LINES TO BE VISUALLY EVALUATED BY ASSESSORS (13, 50 AND 95 MM LONG) (b) SCORE SHEET USED BY

ASSESSORS FOR VISUAL EVALUATION

occurred when measuring scale 199. The error is typical of what can hap pen when measuring with the ruler.

Results from the visual evaluation of length (Experiment 2) are in Table 3. The lowest standard deviations are comparable to those of the mouse and ruler measurements. The mean and highest standard deviations are greater. As expected, this showed that even simple sensory evaluations, like the repeated visual evalua- tion of the same length, are prone to more error than the actual measurement of marks on NLS, whether these be made by the mouse or a ruler.

USING A MOUSE 9

TABLE 3 . AVERAGE f STANDARD DEVIATION OF MEASUREMENTS PERFORMED WITH THE MOUSE AND THE RULER. ALSO PRESENTED ARE RESULTS OF VISUAL EVALUATION

OF LENGTH PERFORMED BY 10 ASSESSORS

Distance on Mouse Ruler Visual evaluation 100 rmn scale readings’ readings’ lowest sdb highest sdb average‘

13 1 2 . 7 2 0.8 1 2 . 9 2 0 . 7 1 2 . 3 2 0 . 5 15.8i 3 . 2 13 .9+ 1 .7

50 4 9 . 1 2 1 . 4 49 .82 1 . 0 44 .92 1 . 5 3 4 . 0 k 6 . 8 43.7+ 3 . 8

95 95 .3* 0 . 9 9 5 . 3 2 0 . 5 1002 O . O d 8 1 . 2 k 6 . 2 9 2 . 3 + 1 . 9

aaverage f standard deviation of 12 readings baverage f standard deviation of 12 readings by the assessors who presented the lowest and highest standard deviations ‘overall average rt mean standard deviation over 10 assessors done assessor evaluated the 95 mm length as equal to the 100 mm ‘very long’ standard, and marked all his evaluations of this line at the end of the scale

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