A COMPARISON OF MBmIPULBTIVE DEXTERITY Ob
EDUCIBBLE MEPIITALLY RETARDED AND NORMAZ
TWELVE TO SIXTEEN YXAR-OLD BOYS
A Pield Report
Presented to
The Graduate Division
Drake University
In Partial Fulfillment
of the Requirements for the Degree
Master of Soience in Education
by
Jerry Leon Richardson
January 1964
A aOMPBRISOH OF MBPaIPULBTIV3 DEXTERITY OF
EDUCABLE MEETTALLY RETARDED AND NORMAL
by
Jerry Leon Richardson
Approved by Committee:
.&ZZzJr. Chairman
, .
; . i . -.' [, . ' 4.. ,
Dean of the Graduate Division
T A B U OF COHTZNTS
OHBPS1ER PAGE
1. IHTBODUCTIQHe * . 1
Source and Selection of Subjects . . . . . . . . 2
Defining the Eduoable Mentally Retarded . . . . 3
I10 S U R W Y O F L I T E B B T ~ O H M O T O R S K I ~ 5
Literature on Motor Skills of the Normal
Popula t ion . . . . . . . . . . . . . . . . . . 5
Literature on Motor Skills of the Retarded
Population . . . . . . . . . . . . . . . . . . 6
111, DESCRIPTIOBI OF TEST AND ANALYSIS OP DATA . . . . . 10 Deeoription o f Purdue Pegboard . . . . . . . . . 10
Teet Procedure and Analysis of D a t 8 . . . . . . 11 IV. SUMMBRY AND OONOLUSIOBS 17
Summary . . . . . . . . . . . . . . . . . . . . 17
Conclusions . . . . . . . . . . . . . . . . . . 20 B I B L I O G R B P W . . , . . . . . . . . . e . e . . e . m . . 22
A P P E W D I X . . . . . . . . . . . . . . . . * . . . . . . * 24
TABLE
LIST OF TABLES
PAGE
I. Test Performance on the Purdue Pegboard by Mentally Retarded Boys in Pontana Junior High Schools, Fontana, California . . . . . . . . 25
11. Test Performance on the Purdue Pegboard by Normal Students at Fontana Junior High School, Fontana, California . . . . . . . . . . . . . . . . . . . 27
111. Statistical Comparison of Gross Manipulative Dexterity Between Retarded and Normal Boys in the Fontana School District, Fontana, California . . . . . . . . . . . . . . . . . . . 29
IV. Statistical Comparison of Fine Manipulative Dexterity Between Retarded and Normal Boys in the Fontana School District, Fontana, . . . . . . . . . . . . . . . . . . . California 30
CHAPTER I
I1BTRODUOTION
During the last ten years vocational guidance became
an important reeponsibil i ty of the special c l a s s f o r the
eduoable mentally retarded, The need of the retarded t o
prepare f o r employment Increased as the need f o r unshilled
l abor decreased due t o teohnologioal development, a p h a s i s
waa placed on identifying aptitude8 which would help the
retarded t o be ae competitive as possible i n the remaining
unskilled l a b o r market.
Placement counselors have indicated t h a t manipulative
dex te r i ty was often a o r l t i c a l fac tor i n job placement. 1
howledge of whether o r not manipulative dexter i ty i s inde-
pendent o f in te l l igence would be of value i n vocational
guidanue. The purpoee of this study was t o determlae whether
a s ignif ioant difference i n manipulative dexter i ty e x i s t s
between educable mentally retarded boys and boys with normal
inte l l igenue,
The Purdue Pegboard was the t e s t ing device used t o
measure manipulative dexteri ty, A conparison of manipulative
dex te r i ty was made by use of a sequence of s t a t i s t i c a l
prooedures: (1) standard e r r o r of the mean, ( 2 ) standard
lEvelJP Murray, "Developing Potential S k l l l s of the Retarded, " Sec- Bview, XXIII (September, 19561, 35-3 .
2
e r r o r of t h e difference between means, and ( 3 ) a t - t e s t of the
d i f f e r ence between meanso1 The n u l l hypothesis was the suppo-
s i t i o n t h a t t he r e i s no s t a t i s t i c a l d i f ference i n t he manipu-
l a t i v e d e x t e r i t y of educable mentally re tarded and normal boys.
I. SOURCE AND SELECTION OF SUBJECTS
The sub jec t s f o r t h i s study were s tudents i n t he
junior high schools of t he Fontana Unified School D i s t r i c t ,
Pontana, Cal ifornia . Pontana, located about f i f t y mi les
e a s t o f Los Angeles, has a population of f i f t e e n thousand
people. Much of the a r ea i n and around Fontana has been
used as grape vineyards o r c i t r u s groves. However, t h e
cha r ac t e r of Fontana has been mostly a f fec ted by t he Kaiser
S t e e l Corporation which employs over 7,000 persons.
Se3ect iop the retarded Era=. A 1 1 boys, a t o t a l of
fo r ty - four , enrol led i n spec i a l c l a sses f o r t h e educable men-
t a l l y r e ta rded , comprised one group. The e t i o l o g i c a l cause
of r e t a r d a t i o n was not a f ac to r i n e s tab l i sh ing t h i s group.
Each sub j ec t had been t e s ted on t he Wechsler In te l l igence
Scale f o r Children within the l a s t two years. The scores
ranged from fif ty- two through seventy-five. The obtained mean
of t h e I n t e l l i g e n c e quot ients f o r t h i s group was 68.61.
The ages of t he subjec ts i n t h i s s tudy were measured
i n months. The chronological age range f o r t he retarded group
was 144 t o 200 months with an average age of 168.56.
l ~ . P. Guilford, Fundamental S t a t i s t i c s in a A Education (New York: M c G r a w - H I 1 1 Book Co., 1950
3
a & p n . Boys enrolled i n
Fontana Junior Htgh sohools, whose age was 144 t o 180, were
glven the Oalifornia Test of Mental Maturity. Those boys
scoring between 105 and 120 were oonsidered e l i g i b l e f o r
the normal group. A t o t a l of ninety boys met botn the age
and in te l l igenoe qualif icat ions. The scores were t a l l i e d
on a frequency dis t r ibut ion. Star t ing from a score of 120,
every second soore t o a t o t a l of forty-four was selected f o r
t he normal group.
A composite picture o f the average age and i n t e l l i -
gence quotients of t he two groups appear i n these resu l t s :
k a IIQ,
Retarded Group 168.56 68.61
lqormal Group 164.34 111.14
11. DEFINIHG THE EDUOQBLE ME1Ql?ALLY REWRDBD
IN THl3 FOHTdna SCHOOL SYSTEM
The Policy of the Fontana Unified School D i s t r i c t ,
Fontana, Oalifornia, has been t o consider those students
scoring between f i f t y and seventy-five on the Wechsler
In te l l igence Scale f o r Children as educable mentally retarded.
If parenta l oonsent was given, the student was placed i n a
spec ia l olase.
General characteristics of behavior have been l i s t e d
f o r the mentally retarded. However, no cha rac te r i s t i c has
sharply dlstingulshed the educable mentally retarded from
the borderline o r d u l l normal individual. The mentally
4
retarded are regarded by Hegge as "eseential ly normal people
whose output of mental a b i l i t y places them a t the lower end
of a d i s t r ibu t ion of normal t r a i t aen l A defini t ion of mental
re ta rda t ion suggested by Sarason has been used t o define
the educable mentally retarded i n the Fontana school system.
Mental retardation re fers t o individuals who, f o r temporary o r long standing reasons, function in t e l l ec - t u a l l y below the average of t h e i r peer groupe; but whose social adequacy i s not i n question or, if' it is i n question, there I s the likelihood that the individual can learn t o f c t ion independently and adequately i n the community, h
IT, 0 , Hegge, nPs~ehologlcal Aspects of Mental Retardation, n V t a t i o q F- ketarded, ed, S, ashington : Gove-ent Pr in t ing Office, 1950).
2seymour B. (&J&~Q a A =, ed. Cliffs, New Jerseyt
QHBPTER I1
SURVEY OF LITEFUTUIE ON MOTOR SKI-
Determining the relationship of intelligence and
motor ability had been the object of various investigations,
Early studies were based on populations with normal intel-
ligence, Braoe reported that studies conducted prior to
1932 indloated little or no correlation between intelligence
and motor ability in the general population for normal
persons,1 Before this time, little effort was made to
identify the educable mentally retarded. Studies comparing
motor ability and mental retardation would have had to use
eubjects from an Institutional population,
1 LITERATURE OBI HOTOR SKILLS
OB THE BORMAL POPULBTION
More recently McCloy and Young found no relationship
between motor ability and intelligence using subjects with
normal intelligence.
Almost no relationship has been found between Intel- ligence quotients and measurements of physical ability. For an indication of ability in physical skills, intelligence quotients are useless scores, at least within the zone of intellectual n nnality that is maintained in the public achools. 8
ID. K. Braoe, "Why Physical Education is a Way of Education," Jourmal of Health and Physical Education, I11 ( De cember , lwr20=53- -
2 ~ . H. McOloy and Norma Young, Tests and Measurements in Phssioal Bducation (New York: Appleton, Oentury, and =fts, 1 9 5 4 ' ) m .
6
Using the Johnson Physical S k l l l Test, Keller drew a
s i m i l a r conclusion. The f lndings indicated t h a t motor a b i l l t y
increases with chronological age, but not wlth mental age o r
In t e l l i gence ~ u o t i e n t . l
Testing 8ubJects from a normal population, Goodenough
found a low-positive relationship between react ion speed and
scores on in te l l igence t e s t s .* l o consistent d i f ferences
appeared i n reaotion speed between children from the upper
and lower socio-economic classes.
11. LITERATURE ON MOTOR SKILLS
OF THE RETARDED POPUUTION
The opinion expressed by re la ted l i t e r a t u r e has been
that a significant difference i n manipulative dex te r i t y
ex i s ted when a comparison was made between normal and mentally
re tarded children. Discussing the mentally retarded, Tredgold
wrote, "Even the best o f them ra re ly a t t a i n t o the precision
and neatness of movements which the ordinary well-trained
ch i ld i s capable. "3
l ~ i n d s e ~ D. Keller, "The Effect of Maturation on Physical S k l l l as Measured by the Johnson Ph s i c a l S k i l l
n Test , Research Quarterly, I X (October, 1938 3 , 54-58.
2Plorence Goodenough, "The Development of the Reactive Process From Early Childhood t o Maturity," Journal a
~ e r u n t a L p s y c u l o a , X V I I I (1935) 1 4 3 1 - 4 5 0 .
3 ~ . F. Tredgold, A J'extbook of Mental D (Baltimore: The Williams and Wilkins Company,
7 Along the same l i n e , Goodenough believed the mentally
re tarded were typ ica l lp awkward and clumsy i n t h e i r movements.'
Sloan concluded tha t the mentally retarded were s ign i f i can t ly
i n f e r i o r i n motor a b i l i t y t o children of normal in te l l igence. 2
However, according t o Hollingsworth, although it was the
exception, the mentally retarded exceed some normals i n motor
a b i l i t y . 3
Studies, c o n ~ a r i n q potor ab i l i t y . Studies comparing
normal and mentally retarded children gave evidence t o the
opinion expressed i n the l i t e r a t u r e of a posi t ive re la t ion-
sh ip between in te l l igence and motor a b i l i t y . I n a comparison
of motor s k i l l s of mentally retarded and normal chi ldren,
Howe found the normal group achieved consis tent ly higher
scores than the retarded group on each t e s t of a ba t te ry of
eleven t e s t s of motor a b i l i t y . H e s ta ted "The differences
were s izeab le and a l l were s ign i f ican t a t the f i v e per cent
l e v e l of confidence. n4
I n a study by Francis and Rarich, 284 mentally retarded
boys and g i r l e were given a bat tery of eleven t e s t s of
l ~ l o r e n c e Goodenough, ~~~~1 Te;;&:j3(Nex York: Rhinehart and Oompany Inc., 19 9 , p.
2 ~ i l l i a m Sloan, " ~ o t o r Prof iciency and Inte l l igence, " icap a m a L p~ Xental DeficiencY, LV ( J a n ~ r ~ s 1951) P -
3 ~ e t a S. Hollingsworth, !Che P S Y C ~ O ~ O K Y 5 Subnoma: u d r e q , (New York: The Macmlllan Company, 192 ) , p . 13
4 ~ l l f f ord C. Howe, " ~ o t o ~ Oharacteris t ics of Mentally Retarded Childreg (Unpublished Doctor's Disser ta t ion, The University of Iowa, Iowa City, 1958).
8
motor a b i l i t y * Data obtained from these t e s t s were oompared
with published norms based on populations of normal children.
The authors suggested a s ignif icant lack of motor a b i l i t y
In t he mentally retarded.
The mentally retarded chlldren I n t h l e invest igat ion were markedly i n f e r i o r t o normal children i n a l l motor performance t e s t s and as age Increased t 4 deviatlons from the normal tended t o become greater.
However, they concluded tha t the motor a b i l i t i e s of the
mentally retarded followed developmental curves s imilar t o
normal children a t lower levels .
Measurements of manipulative dexter i ty were made by
Cantor on a group with an upper in te l l igence quotient of
The r eau l t s indicated a marked l n a b i l l t y by subjects
of the group t o perfom manipulative dexter i ty tasks a s
measured by the Purdue Pegboard.
There seemed t o be agreement among authors that no
re la t ionsh ip ex i s t s between intel l igence and motor a b i l i t y
i n the general population having normal Intel l igence. The
general tenor of l i t e r a t u r e concerned Kith the mentally
l ~ o b e r t J. Prancis and G. Lawrenoe Rarich, Motor m c t e r i s t i o s pf M e n t a u petarded, United Sta tes
Department of Health, Education, and Welfare, Cooperative ~ e s e a r c h Monograph NO. 1, 1960).
2~ordon N. Cantor and C. L. Stacey, "~an ipu la t ive Dexteri ty i n Mental Defectives, Journab a pental Deficiency, LVI (July-August.
9
retarded was that they have a definite lack of motor abi l i ty ,
although there was some overlapping with the normal population.
Recent studies gathering oomparatlve data gave evidence to
this opinion.
CHAPTER I11
DESCRIPTION OF TEST AND ANALYSIS OF DATA
The Purdue Pegboard, a testing device used for this
study, was designed to asslst in the selection of employees
for jobs requiring manipulative dexterity. Such jobs would
probably be routine manual labor but of an exacting nature
such as packing, sorting or assembly.
I. DESCRIPTION OF PURDUE PEGBOARD
Kinds pf measurement obtainable, Separate measures
of movements of the hands, fingers and arms, were established
for the Purdue Pegboard: (1) Right hand, (2) Left hand, and
(3) Both hands.
A separate measure, achieved by assembling pins,
collars and washers was developed. This exacting movement of
the fingers, was named Assembly test.
Test norms. Norms were established on five groups
of subjects: (1) College men, (2) College women, (3) Veterans
(men), (4) Industrial applicants (women), and (5) Industrial
applicants (men). Separate norms were not computed for
high-school students. Industrial norms were used in high-
school vocational guidance since the high school student
would succeed or fail on the job in terms of his standing in
comparison with industrial employees.
11
character ie t ics . Located a t one and of the pegboard were four cups equipped with pins, co l la r8 and
washers. T h e two outside cups each contained twenty-five
pins. The f i rs t cup r i g h t of center, contalned twenty
co l l a r s . The f irst cup, l e f t of center, contained f o r t y
washere, Two rows of holes extended from the cups t he length
of t h e pegboard,
I. TEST PROCEDURE AMD ANALYSIS OF DATA
Measures of manipulative dexter i ty on three t e s t s
were obtained: (1) Right hand, ( 2 ) Left hand, and (3) Both
hands, A cumulative score of these t e s t s was used f o r a
comparison of "gross " manipulative dex te r i ty between the
two groups. The d i rec t ions f o r t e s t administrat ion f o r
these t e s t s were followed as given i n the Examiners Manual
f o r the Purdue Pegboard. 1
wnd t e s t . The object of the Right hand t e s t
was t o t ake a pin with the r i g h t hand from the right-hand
oup, The pin was then inser ted i n the top hole of the
r i g h t hand row, The score was the t o t a l number of pins
i n se r t ed i n t h i r t y seconds.
Only one sub3ect i n the normal group scored lower
than the average f o r the retarded group. A t the opposite
lPurdue Research Foundation, 868- Manual a % n r d u &gboard (Chicago: Science Research Aseociates, 19 ).
12
end of t he range, only two subjects from the retarded group
scored higher than the average f o r the normal group. The
t e s t performance has shoym t h e s e resu l t s :
Range
Mean
&ef t hand t e s t . The tes tee was allowed t h i r t y seconds
t o i n s e r t pins with h i s l e f t hand. The t e s t ee took a pin
with h i s l e f t hand from the left-hand cup. The pin was then
i n s e r t e d i n the top hole of the l e f t hand row. The score
was the t o t a l number of pins inser ted In t h i r t y seconds.
A g rea te r degree of overlapping of scores was obtained
on t h i s t e s t than on any of the other measures. A t o t a l of
four sub jec t s f r o m the normal group scored l e s s than the
average of 13.50 pin inse r t ions of the retarded group.
Scores higher than the average of 15.82 pin inse r t ions of
t he normal group were made by seven subjects of the retarded
group. The t e s t performance has shorn these r e su l t s :
uEle& Retarded
Range 11-19 5-18
Mean 15.82 13-50
band t e s t . This t e s t measured the a b i l i t y o f
both hands working together. The tes tee picked up a pin
from the right-hand cup wlth his r i gh t hand and a t the same
time picked up a pin f r o m the left-hand cup wlth h i s l e f t
13 hand and placed the pin8 dom the rows. The t e s t e e began
w i t h t h e top hole of both rows. If the t e s t ee were l e f t - handed, the di rec t ions were changed by substituting " l e f t
handn f o r "right handn and "r ight handn f o r " l e f t handn
wherever they occurred i n the direct ions. Only the t o t a l
number of pa i r s of pins were counted. The t e s t performance
has shown these resu l t s :
u.Z@iL Retarded Range 10-16 4-16
Mean 13.18 10.70
A t o t a l of four retarded subjects scored higher than
the obtained average f o r the normal group. Only one subject
from the normal group scored lower than the average of the
re tarded group.
#core. A cumulative ecore of the three
t e a t s re fe r red t o as: (1) Right hand, ( 2 ) Left hand, and (3)
Both hands, was used f o r the comparison of "gross" manipulative
dex te r i t y , Some overlapping of scores appeared between the
two groups although the normal group averaged over e ight pin
i n s e r t i o n s per subject more than the retarded group. Only
t h r e e sub jec t s i n the retarded group scored higher than the
average score of the normal group. From the normal group
only two soored l e s a than the average of the retarded group.
The cumulative scores of the t e s t s of ngrossn manipulative
d e x t e r i t y have been shown In these r e s u l t s r
Retarded
Range 38-56 14-55
Mean 46.07 37.73 Standard deviation 3.61 7.72
A sequence of s t a t i s t i c a l procedures was used t o
ob ta in a comparison of t e s t performance: (1) standard e r r o r
of t h e mean, (2 ) standard e r ro r of the difference between
means, and (3) t - t e s t of the difference between means. The
s t a t i s t i c a l data gathered l a the sequence have shown these
r e s u l t s :
Standard e r r o r of the mean .55 normal groups 1.17 retarded group
Standard e r r o r of the difference between means 1.29
t - r a t i o of the difference between means 6.46
A t - r a t i o of 6.46 was s ign i f ican t a t the 1 per cent
l e v e l of confidence. The null hypothesis, which supposes
t h a t the re i s no s t a t i s t i c a l difference i n "gross" manip-
u l a t i v e dex te r i t y of educable mentally retarded and normal
boye, was re lec ted. The inference, with few exceptions, was
t h a t a boy with normal Intel l igence has a grea te r degree of n grossn manipulative dex te r i ty than an educable mentally
re tarded boy.
4sse- t e s t . The Assembly t e s t was used f o r the
measure of "fine" aanlpulat lve dexteri ty. The tes tee took
1 5 a pin from the right-hand cup x i t h h l s r l g h t hand and a
washer from the left-hand cup wlth h i s l e f t hand. The pin was i n s e r t e d i n the top right-hand hole. Then a c o l l a r was
picked up with the r i g h t hand. A s soon as the p in was In-
s e r t ed , t he l e f t hand placed a washer on the pin; then i t
picked up another washer. The r l gh t hand then placed the
c o l l a r over the pin on top of the washer and reached f o r
another pin t o start a new assembly. The l e f t hand placed
a washer on the pin over the co l l a r t o complete the sequence
and picked up a washer f o r the next assembly. Both hands
should be i n motion a t the same time.
The t e s t e r gave a demonstration of the sequence of
movements as the ine t ruc t ions were read verbatim. The t e s t e e
was allowed t o pract ice the required sequence of movement8
u n t i l t he t e s t e r was sure he f u l l y understood the procedure.
The t o t a l number o f pa r t s assembled i n s ix ty seconds was
t he score f o r t h i s t e s t .
Each assembly had four parts. The normal group
averaged over t w o complete assemblies per subject more than
the re tarded group. Only two subjects of the retarded group
scored higher than the obtained average o f the normal group.
811 but one of the normal group scored higher than the
average of the retarded group. Performance of the two groups
on the Assembly t e s t has been shorn i n these r e su l t s :
wJEiL Re tarded Ftangs 27-49 17-44
Mean 37.34 27 91
Standard deviation 4.80 6.81
A comparison of test performance was made through a
sequence of statistical procedures: (1) standard error of
the mean, (2) standard error of the difference between means,
and (3) t-test of the difference between means. The statis-
tical data gathered in this sequence have been shown in these
resulte:
Standard error of the mean ,75 normal group 1.03 retarded group
Standard error of the difference between means 1.27
t-ratio of the difference between means 7.42
A t-ratio of 7.42 was highly significant at the 1 per
cent level of confidence. This indicated rejection of the
null hypothesis that there was no statistical difference in
"finen manipulative dexterity of educable mentally retarded
and normal boys. The inference was that with few exceptions
a boy with normal lntelllgenoe has a higher degree of 'finen
manipulative dexterity than an educable mentally retarded
boy.
CHAPTER 1V
SUMMARY AND CONCLUSIONS
During the last ten years vocational guidance became
an important responsibility of the special class for the
educable mentally retarded. The need of the retarded to
prepare for employment increased as the need for unskilled
labor decreased due to technological development. Emphasis
was placed on Identifying aptitudes which would help the
retarded to be as competitive a8 possible in the remaining
unskilled labor market.
Placement counselors have indicated that manipulative
dexterity wae often a critical factor in job placement.
mowledge of whether or not manipulative dexterity is inde-
pendent of intelligence would be of value in vocational
guidance. The purpose of this study was to determine whether
a eignificant difference in manipulative dexterity exists
between educable mentally retarded boys and boys with normal
intelligence.
So that a comparison of manipulative dexterity could
be made, two samples of forty-four boys each were selected.
All boys enrolled in the special class for the educable
mentally retarded comprised one group. The range of intelli-
gence quotients for this group was from fifty-two to seventy-
five as measured by the Wechsler Intelligence Sumey for
18 Children. The age range, figured i n months, was 144 t o 200
months. Sub jec t s of the normal group, which was made up
of boys of a similar age, scored between 105 and 120 on the
Ca l i f o rn i a Test o f Mental Wtu r i t y .
The Purdue Pegboard was the t e s t i ng device used t o
measure manipulative dexter i ty . S e p a r a ~ measures o f move-
ments of t h e hands, f i n g e r s and arms, were establ ished f o r
t h e Purdue Pegboard: (1) Right hand, ( 2 ) Left hand, and
( 3 ) Both hands. A cumulative score of these t e s t s was used
f o r a comparison of "gross" manipulative dex t e r i t y between
t h e two groups.
A separa te measure, achieved by assembling pins, col-
la rs and washers w a s developed. This exacting movement of
t h e fingers, the Assembly t e s t , was a measure of " f inen
manipulat ive dex te r i ty .
A comparison of manipulative dex te r i ty was made by
use of a sequence of s t a t i s t i c a l procedures: (1) standard
e r r o r of t h e mean, ( 2 ) standard e r r o r o f the dif ference
between means, and ( 3 ) a t - t e s t of the d i f ference between
means. The null hypothesis was the supposition t h a t the re i s
no s t a t i s t i c a l difference i n the manipulative dex t e r i t y o f
educable mentally retarded and normal boys. A t - r a t i o of
2.58, t h e 1 per cent l e v e l of confidence, was needed t o
r e j e c t t he n u l l hypothesis.
,ElI~ht band test. The normal group averaged over th ree
19 p in In se r t i ons Per subject more than the retarded group.
Only two subject6 from t h e retarded group scored higher than
the average of the normal group whereas only one subject
from the normal groups scored lower than the average of the
re tarded group.
&ef t && t e s t . The normal group averaged s l i g h t l y
over two pin i n se r t i ons per subject more than the retarded
group. Seven subjects of the retarded group scored a higher
t o t a l of pin inse r t ions than the average of the normal group.
Four subject8 of the normal group scored a lower t o t a l of
p in i n s e r t i o n s than the average of the retarded group.
p o u m4 t e e t . The normal group averaged s l i g h t l y
over t w o p a i r s of pin Insert ions per subject more than the
re ta rded group, Only one subject from the normal group
scored l e s s than the average f o r the retarded group, whereas
f o u r sub lec t s from the retarded group scored higher than
t h e average f o r the normal group,
Qumulativa m. A cumulative score of the three
t e s t s re fe r red t o as: (1) Right hand, ( 2 ) Left hand, and (3)
Both hands, uas used f o r the comparison of "gross" manipu-
l a t i v e dex te r i ty . The normal group averaged over e ight pin
i n s e r t i o n s per subject more than the retarded group. However,
1% was noted t h a t three subjects i n the retarded group scored
a higher t o t a l of p in inser t ions per subject than the mean
of the normal groUP. A t-ratio of the standard error of
the difference between means was 6.46. This figure was
significant at the 1 per cent level of confidence indicating
rejection of the null hypothesis.
~ n i ~ d a t i v e dexteritr. A measure of the exacting
movement8 Of the fingers was uonsidered to be "fine" manipu-
lative dexterity. This measure, the Besembly test, was
achieved by assembling pins, collars and washers. Plaolng
four separate parts together completed one assembly.
The normal group averaged over two complete asserublies
more than the average of the retarded group. However, two
subjects of the retarded group scored higher than the mean
of the normal group.
A aomparison of the two groupa was made by using the
standard error of the difference between means. A t-ratio
of the difference between means of 7.42 was obtained. Thla
figure was significant at the 1 per cent level indicating
rejeotion of the null hypothesis.
11. CONCLUSION
A t-score as large as that obtained on the t-test
of the difference between means for the comparison for
both "grossn and "finen manipulative dexterity indicated a
highly significant difference in the test performance of
the two groups. The resulting inference was that a boy wlth
normal intelligence wlll perform more ably on simple tasks
of both ''gross" or "finen manipulative dexterity.
The conclusion was made that manipulative dexterity
would not usually be an aptitude which could be used for
purposes of vocational guidance.
4ecommendatiou. The data indicated three subjects
of the group of forty-four retarded boys performed as
efficiently on simple tasks of manipulative dexterity as
boys with normal intelligence. The following procedures were
recommended to improve the vocational guidance of the retarded
who do poseees a no-1 degree of manipulative dexterity:
(1) identify retarded students with a normal degree of
manipulative dexterity, (2) identify jobs in the community
requiring a degree of manipulative dexterity, and (3) eral-
uate the Job performance of those retarded students performing
simple tasks of manipulative dexterity.
BIBLIOGRAPHY
Cantor, Gordon i n Mental Def'lcienclrr , LVI
Prancle, Robert J., Rarich, Lawrenoe G. po tor Charac te r i s t i c s pg $& B e n t a u Office of Education, United S t a t e s Department of Health, Education, and Welfare, OE - 35005, Washington: Government P r in t ing Office, 1960.
Goodenough, Florence. F Test-. Hew York: Rhlnehart and Company Inc., 19 9,
Guil ford , J. Po damental S t a t i s t i c s
Hegge, T. G. "Psychological Aepects of Mental Retardation," VocstlonaL. R e b a g t a t i ~ g pg a M&g&J& Retarded, E d i t e d by S, G, DiMlchael, Washington: Government Pr ln t ing O f f i c e , 1950.
Purdue Research Foundation, e p i n u #& Purdue Pe oard. Chicago :
-Research Associates, 19 R+-
Sarason, Seymour B. P s ~ c h o l o a v a E x c e ~ t l o ~ Children a A u. Edited by William M. Cruickshank. Englewood Cliffs , New Jersey: Prent ice Hall, 1955.
Tredgold, A. B. Textbook a p e n u D e f I c I e ~ . BBltlmore: The Williams and Wilkene Company, 1952. 5 9 pp.
APPENDIX
TABLE I
TEST PERFOFWINCE ON THE PURDUE PEGBOARD
BY MENTALLY RETARDED BOYS IR
FONTANA JUNIOR HIGH SOHOOLS,
FONTANA , OALIFORNIA
la t lve Score
TABLE I
(continued)
Both Hands
Cumulative Score
TABLE I1
TEST PERFOLWNCE ON THE PUFDUE PEGBOARD
BY NORMAL STUDENTS AT
FONTANA JUNIOR HIGH SCHOOL,
FONTANA, CALIFORNIA
Both Hands
Cumulative Score
TABLE I11
Statistic
Number
S T A T I S T I C A L COMPBRISON
OF GROSS MANIPULATIVE
DEXTERITY B E T m E N
RETARDED AND N0RMA.L
BOYS I N THE FONTBNA
SCHOOL D I S T R I C T ,
FONTANA , CALIFORNIA
Standard deviation
Standard error of the mean
Standard error of a difference between means
Normal
44
Retarded
44
statistic
Number
Mean
TABLE IV
S T A T I S T I C A L COMPAXISON
OF FINE MBNIPDLBTIVE
DEXTERITY BETWEEN
RETARDED m N O R .
BOYS I N THE FONTANA
SCHOOL D I S T R I C T ,
FONTANA, CALIFORNIA
Retarded I Standard deviation 4.80 I 6.81
Standard error of the mean .75 1 1.03
Standard error of a difference between means 1.27
t-ratio 7.42
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