Skip to main content
. Author manuscript; available in PMC: 2012 Oct 9.
Published in final edited form as: School Psych Rev. 2012 Fall;41(1):3–22.

Table 3.

Technical Adequacy of Discrepancy/Consistency Method (D/CM)

Ignorable
Differencea 		Important
Differenceb 		Base
Rate %c 		Sensitivityd Specificitye PPVf NPVg E1h E2i
.01   .25 6.3 .19 .97 .33 .95 93.7% 92.5%
  .5 3.2 .27 .98 .27 .98 96.8% 95.0%
  .75 1.4 .47 .97 .18 .99 98.6% 96.3%
1.0 .5 .66 .97 .09 .99 99.5% 97.5%
1.25 .2 .82 .97 .04 .99 99.8% 96.5%
.05   .25 6.9 .19 .98 .37 .94 93.1% 92.1%
  .5 3.6 .31 .97 .31 .97 96.4% 95.0%
  .75 1.6 .47 .97 .21 .99 98.4% 96.3%
1.0 .6 .66 .97 .11 .99 99.4% 96.6%
1.25 .2 .82 .97 .04 .99 99.8% 96.5%
.15   .25 8.5 .19 .98 .46 .93 91.5% 91.2%
  .5 4.6 .31 .98 .39 .97 95.4% 94.6%
  .75 2.0 .48 .97 .28 .99 97.9% 96.3%
1.0 .8 .66 .97 .14 .99 99.2% 96.6%
1.25 .2 .80 .97 .05 .99 99.8% 96.5%
.25   .25 10.2 .19 .98 .54 .91 87.8% 90.2%
  .5 5.6 .31 .98 .48 .96 94.4% 94.3%
  .75 2.5 .48 .98 .34 .99 97.5% 96.3%
1.0 .9 .67 .97 .17 .99 99.1% 96.7%
1.25 .3 .79 .97 .06 .99 99.7% 96.5%
.5     .5 7.4 .32 .99 .65 .95 92.6% 93.7%
  .75 3.3 .49 .98 .45 .99 96.7% 96.3%
1.0 1.2 .66 .97 .21 .99 98.8% 96.8%
1.25 .4 .76 .97 .07 .99 99.7% 96.6%
.75   .75 3.8 .49 .98 .51 .98 96.2% 96.3%
1.0 1.3 .64 .97 .23 .99 98.7% 96.7%
1.25 .4 .74 .97 .08 .99 99.6% 96.6%
1.0   1.0 1.4 .62 .97 .24 .99 98.6% 96.7%
1.25 .4 .71 .97 .08 .99 99.6% 96.5%

Note. These results apply to the 221,598 cases out of 1,000,000 that remained after applying achievement (< 90) and mental ability (> 69) cutoffs. At the observed level there were 8031 cases (3.6%) of SLD and 213,567 (96.4%) of Not SLD.

a

Ignorable Difference is the latent z score difference that is small enough to ignore.

b

Important Difference is the latent z score difference that is large enough to be considered a cause of SLD.

c

Base Rate % is percentage of cases in the sample selected for low achievement but of average mental ability classified as SLD at the latent level.

d

Sensitivity is the proportion of true SLD cases identified as such by the method.

e

Specificity is the proportion of true Not SLD cases identified as such by the method.

f

PPV is Positive Predictive Value or the probability of being truly SLD given a positive test result.

g

NPV is Negative Predictive Value or the probability of being truly Not SLD given a negative test result.

h

E1 is the efficiency or percent of correct classifications made without applying the test. It is equal to 1- Base Rate %.

i

E2 is the efficiency or percent of correct classifications made when the test is used and is the sum of the percent of True Positives and True Negatives.