CS REPORT 4/01 - National Board of Examiners in Optometry

Part I (Basic Science) Examination, December 2002
Statistical Report
National Board of Examiners in Optometry ®
The Part I (Basic Science or BS) examination was administered on December 11-12, at
19 test centers. This was the 33 rd administration of the BS examination since its inception in
1987.
The BS examination is targeted for students entering their third year of optometric
education. Although the August and December administrations are equivalent in content and
difficulty, the overwhelming majority of students sit for the August administration, partially
because it is their earliest opportunity for successful completion. The candidate population for
the subsequent December administration typically has a disproportionate number and percentage
of prior failees. For the December 2002 administration, the total number of candidates (392) and
the number (27) and rounded percentage of “first timers” (7%) were the lowest for any NBEO
BS examination. One candidate was provided accommodations under the Americans with
Disabilities Act (ADA). The immediately preceding administration of August 2002 hosted a
record number of candidates (1608) for any examination that the National Board has ever
administered.
Results
Table 1 displays the number of items administered, and the number of items deleted and
scored. The deletion of items was based on the detection of psychometric flaws during the postadministration
quality-control review.
The distribution of overall test scores is displayed in Figure 1. The examination Part and
section statistics are displayed in Tables 2 and 3, respectively. The data in Figure 1 and Tables 2
and 3 are based on the entire candidate population, rather than on any reference or subgroup of
the population. No scores of any candidate were cancelled because of evidence of cheating.
National Board pass-fail decisions for BS are based on Part performance only. However,
since some state boards require that candidates pass individual sections, the National Board
computes section cutoff scores that are represented by scaled scores of 75. The pass-fail data for
the sections indicate the percentage of candidates who would have failed if the section cutoff
scores had been applied. The National Board advises against requiring that individual sections
be passed.

Basic Science, 12/2002 -2-
Table 1: Number of Test Items Administered and Scored
Number of Test Items
Administered Deleted Scored
O v e r a l l T e s t 435 8 427
Human Biology 195 5 190
Ocular / Visual Biology 90 1 89
Optics 125 2 123
Psychology 25 0 25
Figure 1: Distribution of Overall Test Scores
140
130
120
110
100
90
Frequency
80
70
60
50
40
30
20
10
0
25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
P e r c e n t a g e S c o r e s

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The National Board uses a criterion-based methodology to determine pass-fail standards.
This methodology is based on many detailed consensual judgments by the Board's examination
committees regarding the difficulty of each test item. The difficulty of test items is based on an
analysis of each of the options within the items. This procedure is known as the Nedelsky/Gross
technique. Articles describing this procedure, as well as an empirical study of its effectiveness,
may be obtained by contacting the National Board office.
The Part pass-fail cutoff score is scaled so that it always equals 300. Similarly, for those
states that have subtest requirements, the sections are scaled so that 75 is reported as the cutoff
score. The scaled Part cutoff of 300 is equal to the weighted average of the section scaled cutoff
score of 75. The scaled scores for each section have a range of 0-99, where 0 represents the
lowest score possible (i.e. zero percent correct), and 99 represents the highest score possible (i.e.,
100% correct). The score range for each Part is based on a 100-900 scale, where 100 represents
zero percent correct, and 900 represents 100% correct.
Table 2: Overall Part Summary Statistics*
Raw Score % Score Scaled Score
D e s c r i p t i v e D a t a
Score Range 133-374 31-88 201-707
** Mean Score 253.80 59.44 293.51
Median Score 256 59.95 295.19
Standard Deviation 30.87 7.23
R e l i a b i l i t y D a t a
KR-20 Coefficient 0.91
Kappa Coefficient 0.71
# SEM: All Scores 9.16 2.15
# SEM: Pass-Fail Cutoff Score 9.56 2.24
P a s s - F a i l D a t a
Pass-Fail Cutoff Score 262 61.36 300
** Number (%) Passing 158 (40.31)
Number (%) Failing 234 (59.69)
* Part statistics are based on 427 items and 392 candidates, 27 (6.89%) of whom are students taking
the test for the first time.
** The mean score and pass rate of students taking BS for the first time are 63.49% and 66.67%, respectively.
# Standard error of measurement

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The overall mean score (59%) was the second-lowest in the history of the BS test. The
overall pass rate (40%) was at a record low. These data, and additional analyses, indicate that
the weak performance is the result of a poorly prepared candidate population, rather than any
skewing in test content or difficulty. This poor performance is consistent with the historical
pattern of poor candidate performance in the off-cycle administration; however, with an
unprecedented low percentage of first timers, the typically weak performance was weaker.
Table 3: Section Summary Statistics
Human Biology Ocular / Visual Biology O p t i c s
Psychology
% Scaled % Scaled % Scaled % Scaled
Score Score Score Score Score Score Score Score
D e s c r i p t i v e D a t a
Score Range 31-89 38-92 22-89 27-92 32-86 40-91 44-96 54-96
Mean Score 59.11 72.90 59.26 70.96 58.54 72.99 66.96 76.97
Standard Deviation 7.94 9.57 8.50 10.33
P a s s - F a i l D a t a*
Pass-Fail Cutoff Score 60.53 75 62.92 75 60.16 75 64.00 75
Candidates Passing (%) 43.88 35.71 44.90 67.60
Candidates Failing (%) 56.12 64.29 55.10 32.40
* Based on National Board criteria, candidates pass or fail Parts only, not sections. These section data are relevant only to applicable
state board requirements.
Performance among the four sections was generally poor. The mean score was below
60% for three of the four sections. The only other BS examination in which this occurred was in
April 1997, which was the administration with the lowest mean and prior record low pass rate.
The highest section mean was in Psychology (67%), which typically attains the highest section
mean. However, this section has the fewest number of items, which limits its impact on the
overall BS mean score.
The next administration of the Part I (Basic Science) examination will be in August 2003.