Behavior Research Methods & Instrumentation 1983,15 (5), 549 SCALO: A program to perform Guttman scaling analysis on the Apple II microcomputer ANDREW R. GILPIN University of Northern Iowa, Cedar Falls, Iowa The purpose of the program SCALO is to perform Guttman (1950) scalogram analysis on a set of up to 100 test items with dichotomous responses. The program computes the reproducibility index ("REP"), a statistical test of the significance of the index, and a variety of measures of test reliability. Requirements. The program is written in APPLE- SOFT BASIC and is intended for use on a 48K Apple II microcomputer, although conversion to similar dialects of MICROSOFT BASIC would be fairly straightforward. Depending on the input mode selected ("DATA" statements or disk files), the number of subjects is constrained only by the amount of core memory or the potential file size, respectively; thus, the program can be used to analyze fairly large data sets. The program itself is relatively large, consisting of 278 lines of BASIC code. Input/output options. There are two modes of input: (1) "DATA" statements incorporated in the program itself prior to run time, and (2) data previously stored in a sequential data file, A missing data option is avail- The author's mailing address is: Department of Psychology, University of Northern Iowa, Cedar Falls, Iowa 50614. able. There are also two modes for output: (1) the screen (in which case scrolling is periodically interrupted) and (2) a printer connected to any slot (port). Methodology. The program SCALO scans the data twice. On the first pass, it computes the difficulty index for each of the items and prints out the indexes in the original item order, after sorting by difficulty. Several measures of odd-even reliability are also computed: Pearson coefficient, Spearman-Brown, Kuder- Richardson No. 20, and Guttman (see Helrnstadter, 1964). On the second pass, the program computes Guttman's (1950) "REP" index, as well as the chance REP and two chi-square tests of the significance of the observed REP (Hofmann, 1979). Availability. A program listing and user's notes are available without charge by writing Andrew R. Gilpin, Department of Psychology, University of Northern Iowa, Cedar Falls, Iowa 50614. Copies on diskette (DOS 3.3) may be obtained by sending a blank diskette plus $2 (to cover postage and handling costs) to the same address. REFERENCES GUTTMAN, L. The bosisJorscalogram analysis. In S. A. Stouffer, J. A. Clausen (Eds.], M«ISUrement and prediction. Princeton, N.J: Princeton UnivenityPress, 19S0. HELM8TADTER, G. C. Principles oj psychological m«ISUrrment. NewYork:Appleton-Century-Crofts, 1964. HOFMANN, R. J. On testing a Guttman scale for significance. Ed- ucational andPsychological M«ISUrrment, 1979,39,297-301. (Manuscript acceptedfor publicationSeptember 23, 1983.) 549 Copyright 1983 Psychonomic Society, Inc.

SCALO: A program to perform Guttman scaling analysis on the Apple II microcomputer

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Behavior Research Methods & Instrumentation1983,15 (5), 549

SCALO: A program to perform Guttmanscaling analysis on the Apple II

microcomputer

ANDREW R. GILPINUniversity ofNorthern Iowa, Cedar Falls, Iowa

The purpose of the program SCALO is to performGuttman (1950) scalogram analysis on a set of up to100 test items with dichotomous responses. The program computes the reproducibility index ("REP"), astatistical test of the significance of the index, and avariety of measures of test reliability.

Requirements. The program is written in APPLESOFT BASIC and is intended for use on a 48K Apple IImicrocomputer, although conversion to similar dialectsof MICROSOFT BASIC would be fairly straightforward.Depending on the input mode selected ("DATA"statements or disk files), the number of subjects isconstrained only by the amount of core memory or thepotential file size, respectively; thus, the program canbe used to analyze fairly large data sets. The programitself is relatively large, consisting of 278 lines of BASICcode.

Input/output options. There are two modes of input:(1) "DATA" statements incorporated in the programitself prior to run time, and (2) data previously storedin a sequential data file, A missing data option is avail-

The author's mailing address is: Department of Psychology,University of Northern Iowa, Cedar Falls, Iowa 50614.

able. There are also two modes for output: (1) thescreen (in which case scrolling is periodically interrupted) and (2) a printer connected to any slot (port).

Methodology. The program SCALO scans the datatwice. On the first pass, it computes the difficultyindex for each of the items and prints out the indexes inthe original item order, after sorting by difficulty.Several measures of odd-even reliability are also computed: Pearson coefficient, Spearman-Brown, KuderRichardson No. 20, and Guttman (see Helrnstadter,1964). On the second pass, the program computesGuttman's (1950) "REP" index, as well as the chanceREP and two chi-square tests of the significance of theobserved REP (Hofmann, 1979).

Availability. A program listing and user's notes areavailable without charge by writing Andrew R. Gilpin,Department of Psychology, University of NorthernIowa, Cedar Falls, Iowa 50614. Copies on diskette(DOS 3.3) may be obtained by sending a blank disketteplus $2 (to cover postage and handling costs) to thesame address.

REFERENCES

GUTTMAN, L. ThebosisJorscalogram analysis. In S. A. Stouffer,L.Gmtman,E.A.Suchman,P.F.~nfdd,S.A.S~,&

J. A. Clausen (Eds.], M«ISUrement and prediction. Princeton,N.J: PrincetonUnivenityPress, 19S0.

HELM8TADTER, G. C. Principles oj psychological m«ISUrrment.NewYork:Appleton-Century-Crofts, 1964.

HOFMANN, R. J. On testinga Guttman scalefor significance. Educational andPsychologicalM«ISUrrment, 1979,39,297-301.

(Manuscript acceptedfor publicationSeptember 23, 1983.)