The Reliability and Validity of the Wallin Peg Boards
The Psychological Clinic Copyright, 1927, by Lightner Witmer, Editor Vol. XVI, No. 7 October, 1927 :Author: Florence L. Goodenough
Institute of Child Welfare, University of Minnesota The Wallin series of performance tests designed for use with very young children consists of four boards, each measuring 3 by 14 inches, % of an inch thick. Each board contains recesses for 6 pegs, similar in size but varying as to form. Board A includes only round pegs, Board B only square pegs, in Board C three round and three square pegs are arranged in alternating sequence, while in Board D there are two round, two square, and two triangular pegs, also arranged alternately. The round pegs are % of an inch in diameter; the square and the triangular pegs are % of an inch on a side. All pegs are 2y2 inches in length. The recesses correspond to the pegs in form, and are % of an inch deep.
At least three previous investigators have published material dealing with the use of these pegs. The original report by Wallin1 is based upon results obtained from 101 subjects ranging in age from 9 months to a little over 8 years. Wallin shows that the four boards constitute a graded series, increasing in difficulty from Board A to Board D. He finds that the ability measured by the boards is one which increases with age: the older children being able to place the pegs in the proper recesses in a shorter time and with fewer errors than the younger children. Tentative age norms are included in the report, but because of the small number of cases at each age, these can be regarded as suggestive only. No data as to the reliability of the test or its correlation with other measures of ability are given.
Baldwin and Stecher2 gave the test to 59 children ranging in age from 2 to 6 years. Of these 22 were tested four times at two week intervals. Some improvement on the later occasions as com1 Wallin, J. E. W.: The Peg Form Boards. Psychol. Clinic, 1918, 12, 40-53.
2 Baldwin, Bird and Stecher, Lorle: The Psychology of the Pre-School Child. D. Appleton and Co., 1925. See pages 77-80. pared to the first is reported, but the correlations between the successive tests are not stated. No correlations with other tests are reported, but age norms in terms of average time required for a successful performance are given for each of the four boards separately. Since the method employed for administering the test differs from that used by Wallin, the results obtained in the two studies cannot be compared directly.
Boards A and B are included in the Stutsman series of performance tests for children of pre-school age.3 Percentile norms upon the performance of approximately 50 children in each of three age groups?18 to 23.5 months, 24 to 29.5 months, and 30 to 35.5 months?are given. A steady decrease from age to age in time required for a successful performance is shown. No data on reliability or correlation with other tests are given. In the study about to be described, the test was given to 100 two-year-olds, 100 three-year-olds, and 100 four-year-olds?300 cases in all?selected to constitute a representative sampling of the population of Minneapolis, on the basis of a comparison of the distribution of paternal occupations within each of the three age groups with that reported for the city as a whole in the 1920 census.4 Exactly 50 boys and 50 girls were included within each age group. Ages were taken to the nearest birthday. Immediately following the peg board tests, all children were given the Kuhlman Revision of the Binet tests. The results obtained from the Kuhlman tests are reported elsewhere.5 Since no alternative form of either test is available, reliability could be studied only by means of retests. The children were therefore re-examined after an average interval of six weeks.6 Both the peg boards and the Kuhlman were given on each occasion; the pegboards invariably being given first. Two examiners, the writer and Miss Mildred Buffington, research assistant in the Institute, made all the tests. In order to gain some information as to the effect of a change of examiners upon the test score, the following plan was carried out: In each age group, 25 of the cases were examined by the 8 Stutsman, Rachel: Performance Tests for Children of Pre-School Age. Genetic Psycliol. Mono., 1926, Vol. 1, No. 1.
4 For a more detailed account of the method of selecting the cases, the reader is referred to The Kulilman-Binet Tests for Children of Pre-School Age, A Critical Study and Evaluation, by Florence L. Goodenough, University of Minnesota, Institute of Child Welfare, Monograph Series No. 2.
6 Ibid.
6 The standard deviation of the interval between tests was 1.5 weeks. writer on both occasions, 25 by Miss Buffington on both occasions, 25 were examined first by the writer, then by Miss Buffington, and the remaining 25 first by Miss Buffington, then by the writer. All examinations were made in a separate room where freedom from interruption could be insured. The tests were given with the child seated at a low table which was placed at the left of a single pedestal desk at which the examiner sat. The following procedure was used:
After any initial shyness had been overcome, and when the child seemed to be entirely at ease, the examiner asked, “Now wouldn’t you like to see some of my blocks?” (The word blocks was used in preference to pegs since it is more familiar to little children.) Board A was then placed on the table before the child with the pegs in place, the long edge of the board parallel to the edge of the table. The examiner then continued, ‘’ See these sticks ? Each one has its own little house. Let’s take them out of their houses.” The examiner then removed the pegs, encouraging the child to help. As the pegs were removed, they were placed at the side of the board away from the child, the examiner taking care to prevent them from rolling out of reach. When all the pegs had been removed, the examiner said, “Now I want to see how fast you can put them all back again. Hurry up, put them back as fast as you can.” If the child did not seem to comprehend what was wanted, the examiner illustrated with one or two pegs which were then removed and the instructions repeated. As soon as the child attempted to put the first peg into a hole, the stop watch was started and the time required for placing all the pegs correctly was recorded. Preliminary adjustment to the situation, fingering the pegs, holding them up for the examiner’s approval, etc., was not included in the time record. Children under three cannot be depended upon to start on signal, but once begun they will usually continue without intermission until the task is completed. For this reason, a time record taken from the beginning of the actual attempt, i.e., from the time when the first peg touches the board, is likely to be a more stable measure than one taken from the pronouncing of a signal word or from the time when the first peg is touched, since the signal word is frequently ignored, or the peg merely taken up and played with.
The children were not urged to greater speed during the placing of the pegs, since this is likely to lead to mental confusion and consequent increase in the number of errors, especially with the boards containing more than one form of the pegs. The only exception to this rule was made in the case of children who stopped to talk or who interrupted their performance for other reasons. In such cases the examiner recalled his attention by a gesture toward the board, saying, ‘’ Go ahead, hurry up, see how fast you can put them all back.” Liberal praise was given as each board was completed, and an occasional word of encouragement or praise during the placing of especially difficult pegs. Boards B, C, and D were given in the same manner as Board A. If a child placed a peg in the wrong hole, no comment was made at the time, but when the remaining holes had been filled as far as possible and the child found himself with a peg left over with no recess into which it could be fitted, the examiner said, ‘’ It won’t go in, will it? Look at the rest of them”?passing a hand along the board but taking care not to point out the error?”and see if you can find what is the matter.’’ If the child then perceived his error he was permitted to correct it; if not, the board was counted as failed. Only a single suggestion of this sort was given.
The boards were always presented in the same order, and one trial was allowed on each. In this study, a time limit of two minutes was allowed for each board, but when the data were worked up, it was found that nothing was added to the accuracy of the test by counting time over 100 seconds each for Boards A and B, and 60 seconds each for C and D.
Errors were also recorded, but, as penalizing for errors was found to lower the reliability of the score, no account has been taken of them in the scoring method finally adopted. Both examiners felt the error score to be an unreliable measure in itself, because of the many marginal cases when a child makes a tentative attempt to place a peg in the wrong recess but withdraws it almost instantly. Such cases are often overlooked if the child moves quickly, and at all events, to assign equal weight to such a performance as to one in which the child persists for a long period in attempting to force a square peg into a round hole is a procedure which it is difficult to justify on any common-sense basis; while in the absence of an automatic recording device it is difficult, if not impossible, to differentiate as to types of error. Since time is in part a function of error, and since the time score is affected not simply by the number of errors but also by their duration, it is perhaps not surprising to find that the time score alone is a more reliable and presumably a more valid measure of a child’s performance than a combined
Table I Medians and 10~00 percentile ranges of time required for success on each of the four boards by half year age groups. Age (months)1 Board A Number of cases Median time (seconds) 90 percentile 10 percentile Board B Number of cases Median time (seconds). 90 percentile 10 percentile Board C Number of cases Median time (seconds) 90 percentile 10 percentile Board D Number of cases Median time (seconds). 90 percentile 10 percentile 18-23.5 Test 1 Test 2 49 49.3 27.0 DNC2 49 94.2 39.2 DNC2 49 DNC2 44.5 DNC2 49 DNC2 DNC DNC 49 40.6 24.5 77.0 49 59.2 35.6 DNC 49 DNC 49.5 DNC 49 DNC DNC DNC 24-29.5 Test 1 51 31.0 25.8 47.8 51 42.7 27.5 89.3 51 DNC 34.8 DNC 51 DNC 59.7 DNC Test 2 51 30.8 19.7 43.3 51 37.8 24.8 53.3 51 DNC 36.5 DNC 51 DNC 49.7 DNC 30-35.5 Test 1 Test 2 51 26.5 17.6 38.3 51 33.3 23.3 70.7 51 72.0 26.5 DNC 51 DNC 44.7 DNC 51 24.1 15.1 34.2 51 31.3 19.6 59.3 51 40.8 21.2 DNC 51 94.5 29.8 DNC 36-41.5 Test 1 Test 2 49 21.4 15.0 34.4 49 27.8 15.9 47.5 49 32.5 20.1 DNC 49 51.2 25.9 DNC 49 19.3 12.6 27.5 49 22.8 14.6 34.4 ?> r” 49 24.1 16.0 54.6 49 32.6 20.2 DNC 42-47.5 Test 1 Test 2 48 17.7 11.2 24.6 48 21.0 14.3 29.8 48 24.1 15.9 69.8 48 34.4 21.3 DNC 48 17.4 10.6 23.7 48 19.9 13.7 33.2 48 23.4 14.7 39.8 48 27.7 17.4 69.5 48-53.5 Test 1 Test 2 52 15.4 10.2 23.9 52 16.6 10.9 23.8 52 19.5 12.6 36.2 52 27.7 16.5 69.5
1 At the time of the first test. 2 DNC?Did not complete. 204 THE PSYCHOLOGICAL CLINIC time-and-error score in which all errors are given equal weight, or than an error score alone. At the beginning of the study, three trials were given on each board. This is the method followed by Wallin and by Stutsman. After about 30 cases had been tested, the second and third trials were discontinued, since many of the children found the later trials quite irksome, and in a few instances an unfavorable emotional reaction ensued which persisted throughout the examination. Stutsman reports a similar difficulty with several of her cases. It was found, moreover, that the correlation between the time required for the entire series on the first trial, and time on the best trial was above .9 for this group of 30 cases. With only a single trial on each board, practically all the children enjoyed the test greatly.
Table II Reliability of the separate boards by age. Age 2 Age 3 Age 4 PE PE PE Board A .720 .032 .661 .038 .395 .057 B .640 .040 .619 .042 .431 .055 .317 .061 .522 .049 D .432 .055 .376 .058
Table I shows the median and the 10-90 percentile range of time required to complete each of the four boards by half year age groups.7
Table I shows a steady decrease with age in time required for a successful performance on each of the boards. It also corroborates Wallin’s findings as to the comparative difficulty of the four boards. A slight effect of practice is seen when the median scores on the second test are compared with those earned six weeks previously, making allowance for the difference in age. This effect is, how7 Because of undistributed failures at the lower extreme, these measures have been used in preference to the mean and standard deviation. See Statistical Method by T. L. Kelley, Macmillan and Co., 1923, pages 75-77. ever, less marked than was found for the Binet tests given at the same sitting.8
Table II shows the reliability of each of the four boards, calculated by means of the correlation between the time scores on each of the two tests. The Pearson product moment formula was used. The data have been treated by age groupings of one year. Boards A and B are seen to be more reliable, on the average, than Boards C and D. This is in part a result of the fact that the test appears to be better suited to the study of two-year-olds than of older children, and, ? as was shown in Table I, only a small percentage of the two-year-olds succeed with Boards C and D.
Table III
Correlations between Kuhlman-Binet mental age and score on each of the four peg boards * Age 2 Age 3 Age 4 PE PE Board A + .457 + .053 + .289 ?.062 + .373 PE ?.058 B + .473 ?.052 + .391 ?.057 + .277 ?.062 + .422 ?.055 + .402 ?.058 D + .417 ?.056 +.482 ?.051
Based upon the results of the first test.
Table III shows the correlation between Kuhlman-Binet mental age and time required for success on each of the four boards. The data are based upon the first of the two examinations given. In deriving a combined score, a rough attempt was made to weight the time scores on the separate boards both with reference to their reliability and their correlation with the Binet mental age. It is obvious that the data do not warrant too great refinement of treatment, since the time scores are affected by many accidental factors which disturb the results in individual cases, and for which clinical allowance must always be made. The method employed is based upon an inspection of the data in Tables I-III and weighting in round numbers according to average reliability, correlation with ? Previous reference.
Binet, and low variability. Four different approximations, one of which involved a combined time-and-error score were tried. The method which was found to show the highest average reliability and correlation with Binet at the various ages is expressed by the following formula: Score = Time on Board A -f- time on Board B + y2 time on Board C -J- J/3 time on Board D. Maximum time allowance, Boards A and B?100 seconds each. Maximum time allowance, Boards C and B? 60 seconds each. Maximum combined score = 250. Figure 1 shows the median combined score on the four boards by age and sex on each of the two examinations. Allowance is made for the gain in age. The data of Figure 1 are given in Table IV. Figure 2 shows the median scores according to Kuhlman Binet mental age. Figure 3 shows the medians for each of the four boards separately.
letoitf ? Z4to?95 JOtom 3bto415 42to 47.5 4dta%5 54t0m Cfironological aye in months Fig. 1.
A tendency toward negative acceleration is very apparent in the curves on each of the separate boards. This tendency is somewhat masked in the combined score, owing to the fact that, since the boards constitute a graded series, the periods of most rapid gain do not coincide, so that slow improvement on the easier boards is compensated for by rapid gain on the more difficult ones. Table V shows the correlation between scores earned on the first and second examinations by age and sexes separately. The corresponding figures for the Kuhlman-Binet are given for comparison. At age two the test compares very favorably with the Kuhlman, as far as reliability is concerned. At ages three and four, it is less reliable, but even here the figures are sufficiently high to ?10 3b 4Z Mental Age in Months Fig. 2.
warrant its use as a supplementary measure, especially in the case of children with a language handicap. Since the total time required for the four boards is rarely over five minutes, the test can readily be given at the same sitting as a Binet without danger of overfatiguing the child.
Table VI shows the correlation between the total score earned on the four boards and Kuhlman-Binet mental age for each of the Test! Test Z Board C Board D V? I Test 1 Test 2 _l 18 50 4Z 5418 30 42 54 Age in months Age in months Fig. 3. WALLIN PEG BOARDS 209 Table IV Medians and 10-90 percentile ranges of combined scores on the four boards by half year age groups. Age (months) 18-23.5 24-29.5 30-35.5 36-41.5 42-47.5 48-53.5 Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls Test 1 Median score… 90 percentile…. 10 percentile Test 2 Median score… 90 percentile 10 percentile 163.5 103.6 247.8 153.0 103.5 221.3 174.8 121.5 250.0 159.7 106.7 214.0 122.2 88.6 146.7 112.7 74.8 146.8 135.6 103.0 182.7 121.0 96.6 160.8 109.8 75.9 151.8 103.0 61.8 145.6 106.9 81.1 150.0 91.7 57.9 125.5 84.3 51.4 126.7 63.4 43.8 83.2 92.2 60.1 130.9 79.8 53.0 123.3 66.7 66.8 60.0 50.0 43.7 45.7 42.5 34.3 97.9 84.0 82.1 70.7 59.0 61.3 56.1 43.6 38.3 42.9 44.0 33.7 90.3 89.3 66.1 53.9
two examinations. It appears from these correlations that the mental functions measured by the two tests are not entirely identical, though they evidently have much in common. Even when correction is made for the unreliability of measurement (correction for attenuation) the relationship is still far from perfect; averaging slightly above .7 for the various groups. It is doubtful whether
Table V Correlation between Scores earned on the First and Second Tests by Age and Sex. Age 2 Age 3 Age 4 Boys Peg boards r PE .913 .016 Girls Boys Girls Boys Girls .675 .052 .751 .042 .625 .058 .457 .075 .709 .048 Kuhlman-Binet r PE .810 .033 .706 .048 .817 .032 .902 .018 .832 .029 .809 .033
tests of this sort, even though their reliability were to be greatly improved, should be looked upon as the equivalent of a Binet test. They supplement the Binet, but do not precisely duplicate it, either in form or significance.
Table VI Correlation between Kuhlman-Binet Mental Age and Total Score on the four boards. Age 2 Boys Girls Age 3 Boys Girls Age 4 Boys Girls Test 1 Test 2 .566 .488 PE PE .065 .073 .469 .432 .074 .078 ,506 .539 PE .071 .067 .596 .587 PE .061 .063 ,428 ,412 PE .078 .079 .496 .559 PE .072 .065
Additional evidence as to the significance of a test is afforded by a study of the amount of overlapping between successive chronological or mental age groups. Tables VII and VIII show these facts for our group of 300 cases. The data are based upon the first of the two examinations given.
WALLIN PEG BOARDS 211
Examination of Tables VII and VIII shows that the amount of overlapping between age groups is relatively small, and is somewhat less when the division is made upon the basis of mental age than when chronological age is used. Moreover, the amount of overlapping increases roughly in proportion to age.9 Effect of a change in examiners upon the test score. The work of testing was divided between two examiners according to a defiTable VII Percentage of each half year chronological age group equalling or exceeding the median of each successive chronological age group. 1-6 to 1-11.5 (Mdn. = 171) 2-0 to 2-5.5 (Mdn. = 124) 1-6 to 1-11.5 Mdn. = 171 50.0 89.1 2-0 2-5.5 Mdn. = 124 2-6 2-11.5 Mdn. = 102 16.7 50.0 3.7 13.0 3-0 3-5.5 Mdn. = 81 3-6 3-11.5 Mdn. = 65 2.2 4-0 4-5.5 Mdn. = 51 Cases 49 51 2-6 to 2-11.5 (Mdn. = 102) 98.0 82.3 50.0 11.8 2.0 51 3-0 to 3-5.5 (Mdn. =81) 98.0 90.0 75.5 50.0 28.6 4.1 49 3-6 to 3-11.5 (Mdn. =65) 4-0 to 4-5.5 (Mdn. = 51) 100.0 100.0 97.9 81.3 50.0 20.8 48 100.0 98.1 98.1 96.2 76.9 50.0 52
nitely laid out plan which was described in an earlier paragraph. A statistical study of the findings shows no consistent difference in the results obtained which can be attributed to a change in examiners, either for the peg boards or the Kuhlman Binet which was given at the same time. The results on the peg boards may be summarized briefly in the following statement: When both tests were made by the same examiner, the median change in total score ? See Mental Tests by Frank N. Freeman, Houghton Mifflin Co., 1926, page 280.
Table VIII Percentage of each half year mental age group1 equalling or exceeding the median of each successive mental age group. Under 2-0 Mdn. = 193 2-0 to 2-5.5 Mdn. = 122 2-6 to 2-11.5 Mdn. = 108 3-0 to 3-5.5 Mdn. 3-6 to 3-11.5 Mdn. = 68 4-0 to 4-5.5 Mdn. = 64 4-6 to 4-11.5 Mdn. = 53 5-0 to 5-5.5 Mdn. = 50 5-6 and over Mdn. = 44 Under 2-0 Mdn. = 193) 2-0 to 2-5.5 (Mdn. = 122) 2-6 to 2-11.5 (Mdn. = 108) 3-0 to 3-5.5 Mdn. =88) -6 to 3-11.5 (Mdn. =68) 4-0 to 4-5.5 Mdn. = 64) 4-6 to 4-11.5 (Mdn. =53) 5-0 to 5-5.5 (Mdn. =50) 5-6 and over (Mdn. =44) 50.0 98.2 100.0 100.0 100.0 100.0 100.0 100.0 100.0 9.3 50.0 67.3 92.1 100.0 100.0 100.0 100.0 100.0 7.0 27.8 50.0 89.5 100.0 91.7 100.0 100.0 3.7 25.0 50.0 96.4 80.5 100.0 100.0 1.9 31.6 50.0 58.3 80.0 83.3 1.9 23.7 35.7 50.0 76.0 83.3 1.9 7.8 14.3 22.2 50.0 55.6 7.8 14.3 19.4 32.0 50.0 2.7 7.1 2.8 20.0 27.7 43 54 52 38 28 36 25 18 100.0 100.0 100.0 100.0 100.0 83.3 50.0
1 Tiy given on tve same day. amounted to a gain of 8.4 points; when there was a change of examiners, the corresponding change was 9.4 points. The difference of one point is well within the limits of chance, and its unreliability is further demonstrated by the fact that the direction of difference is not the same at all ages, and is always small in amount. Nevertheless, since only two examiners were involved, the findings obviously do not warrant wide generalization. They merely serve to show that under uniform testing conditions, reasonably competent examiners who follow a common procedure can secure essentially similar results. Sex differences. Figure 1 shows the gain in total score from age to age for sexes separately on each of the two examinations. The curves for the second examination have been moved forward to allow for the difference in age.
It is seen that sex differences are very small, but that the boys are, on the average, slightly more accelerated than the girls. Figure 2 shows that this is also true when the groups are divided on the basis of mental age instead of chronological age. On the Binet tests given to the same children, the sex differences were also small, but the general tendency was in the opposite direction, i.e., toward a slight superiority of the girls. Both findings are in general agreement with those which have been reported for elementary school children, where the girls, as a rule, show some superiority over the boys in tests of the Binet type, while boys are more likely to excel in form board tests.
Socio-economic differences. It was stated in an earlier paragraph that the children were selected to constitute a representative sampling of the population of Minneapolis. The basis of selection was paternal occupation. On the Kuhlman tests given to the same children on the same days, a very marked difference was found to exist between the average performance of children belonging to the different occupational classes. On the peg board tests, no such differences are apparent. When the average performance of the children belonging to the upper half of the occupational distribution is compared with that of the lower half, it is found that on the first test the children of the lower occupational groups do slightly better than those of the upper groups; on the second test the upper groups excel, but in neither case is the difference great enough to be reliable nor does it follow a consistent direction at the different age levels. Even when the performance of the children of day la214 THE PSYCHOLOGICAL CLINIC borers is compared with that of the children whose fathers belong to the professional classes, no reliable differences were found. On the Kuhlman-Binet, the superiority of the professional group amounted to approximately one and one-fourth standard deviations of the total distribution of scores for the 300 cases. This difference in the social distribution of the abilities measured by the two methods must be regarded as highly significant. Since exactly the same children were used as subjects for both tests, and since the measurements were taken on the same day, the results cannot be explained on the basis of a difference in sampling. While the reliability of the peg boards is not sufficiently high to permit more than tentative classification of individuals, it is adequate for differentiation between groups. For two-year-old children, it appears to be quite as reliable as the Kuhlman-Binet at the same age level. This makes it possible to compare the standing of contrasted social groups in respect to the two types of ability by means of equally reliable measures applied to the same subjects. In average standing on the Kuhlman-Binet, the two-year-old children whose fathers belong to the professional classes exceed the children of day laborers by approximately one and one half standard deviations of the total distribution of ratings for the year group. On the peg boards, the children of day laborers exceed the children of the professional classes, but the difference is less than one tenth of a standard deviation of the total distribution of scores at that age.
These data tend to confirm the conclusion which was drawn from the table of correlations, that entirely apart from the question of comparative reliability, the two tests do not measure precisely similar mental functions. It would seem that the Kuhlman measures certain functions not measured by the peg boards, the distribution of which among the general population is skewed toward the upper occupational levels; while the peg boards appear to measure certain functions not measured by the Kuhlman which are more evenly distributed throughout the population. Our data do not permit us to judge the nature of these functions, though it might be noted in passing that the results of certain tests for mechanical ability recently standardized at the University of Minnesota show a similar lack of relationship to social status. It may be that the peg board performance is in some degree related to mechanical aptitude, the Binet to potential scholastic achievement. This hypothesis is plausible, but it has not been verified.
Summary 1. The Wallin peg boards, Series A-D inclusive, were given to three groups of 100 children each, whose ages, taken to the nearest birthday, were two, three, and four years, respectively. These children were selected to constitute a representative sampling of the population of Minneapolis on the basis of a comparison of the distribution of paternal occupations with that reported for the city as a whole in the 1920 census. Exactly 50 boys and 50 girls were included in each age group. 2. Since no alternative form of the test is available, all children were re-examined after an average interval of six weeks. The reliability of the test was determined by correlating the scores earned on the two occasions. At age two the reliability was found to be .794; at age three, .688; at age four, .583.
3. The average correlation with the Kuhlman-Binet given on the same day was .507 for single year age groups. There is little difference in the correlations obtained at the various ages. 4. The amount of overlapping of the scores increases approximately in proportion to age. 5. A change in examiners does not necessarily affect the test score, if the testing procedure and examining conditions are uniform. 6. Sex differences in the test performance are small, but in general tend to favor the boys.
7. Children from different socio-economic levels do about equally well on this test, although they show marked differences in their performance on the Kuhlman-Binet. Possible explanations for this discrepancy are discussed.
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