Adapted from: Assessment in Special and inclusive education Salvia, Ysseldyke, Bolt. Module 2 Technical Prerequisites for Understanding Assessments Prerequisites for Understanding Assessments   Descriptive Statistics: A description of what generated data shows. Descriptive statistics aim to summarize basic quantitative concepts. Descriptive statistics include the following: 1. Scales of measurement: Ordinal scale: allows for rank order (1st, 2nd, 3rd, etc.) by which data can be sorted, but does not allow for relative degree of difference between them. Equal interval scale: also rank orders things, however, the magnitude of difference between values is known (i.e., measurement of time, length, weight, etc.) Prerequisites for Understanding Assessments   Sets of equal-interval scores( student scores on a classroom test) can be described in terms of four characteristics: (1) Mean –Arithmetic average (2) Variance – dispersion of a set of scores around the mean of distribution (3) Skew – asymmetry in a distribution (the distribution does not follow the NCE) Note the samples in the following frames: Prerequisites for Understanding Assessments   A distribution is skewed if one of its tails is longer than the other. The first distribution shown has a positive skew. This means that it has a long tail in the positive direction. Prerequisites for Understanding Assessments   The distribution below it has a negative skew since it has a long tail in the negative direction. the third distribution is symmetric and has no skew. Prerequisites for Understanding Assessments (4) Kurtosis: how high a curve rises, the peakedness of a curve. Prerequisites for Understanding Assessments Validity Validity: the degree to which a test measures what it is supposed to measure. There are three basic approaches to the validity of tests and measures as shown by Mason and Bramble (1989). These are content validity, construct validity, and criterion-related validity. Content Validity: This approach measures the degree to which the test items represent the domain or universe of the trait or property being measured. In order to establish the content validity of a measuring instrument, the educator must identify the overall content to be represented. Prerequisites for Understanding Assessments Construct Validity: the extent to which a test measures a theoretical trait or characteristic. Criterion related validity: extent to which a person’s score on a criterion measure can be estimated from that persons score on a test of unknown validity. Prerequisites for Understanding Assessments Reliability Reliability: concerns the extent to which the instrument yields the same results on repeated tr.

1. Adapted from: Assessment in Special and inclusive education
Salvia, Ysseldyke, Bolt.
Module 2
Technical Prerequisites for Understanding Assessments
Prerequisites for Understanding Assessments
Descriptive Statistics: A description of what generated data
shows. Descriptive statistics aim to summarize basic
quantitative concepts. Descriptive statistics include the
following:

2. 1. Scales of measurement:
Ordinal scale: allows for rank order (1st, 2nd, 3rd, etc.) by
which data can be sorted, but does not allow for relative degree
of difference between them.
Equal interval scale: also rank orders things, however, the
magnitude of difference between values is known (i.e.,
measurement of time, length, weight, etc.)
Prerequisites for Understanding Assessments
Sets of equal-interval scores( student scores on a classroom
test) can be described in terms of four characteristics:
(1) Mean –Arithmetic average
(2) Variance – dispersion of a set of scores
around the mean of distribution
(3) Skew – asymmetry in a distribution (the
distribution does not follow the NCE)
Note the samples in the following frames:
Prerequisites for Understanding Assessments

3. A distribution is skewed if one of its tails is longer than the
other. The first distribution shown has a positive skew. This
means that it has a long tail in the positive direction.
Prerequisites for Understanding Assessments
The distribution below it has a negative skew since it has a long
tail in the negative direction.
the third distribution is symmetric and has no skew.
Prerequisites for Understanding Assessments
(4) Kurtosis: how high a curve rises, the peakedness of a
curve.

4. Prerequisites for Understanding Assessments
Validity
Validity: the degree to which a test measures what it is
supposed to measure. There are three basic approaches to the
validity of tests and measures as shown by Mason and Bramble
(1989). These are content validity, construct validity, and
criterion-related validity.
Content Validity: This approach measures the degree to which
the test items represent the domain or universe of the trait or
property being measured. In order to establish the content
validity of a measuring instrument, the educator must identify
the overall content to be represented.
Prerequisites for Understanding Assessments
Construct Validity: the extent to which a test measures a
theoretical trait or characteristic.
Criterion related validity: extent to which a person’s score on a
criterion measure can be estimated from that persons score on a
test of unknown validity.

5. Prerequisites for Understanding Assessments
Reliability
Reliability: concerns the extent to which the instrument yields
the same results on repeated trials.
Retest Method : the same test is given to the same people after a
period of time. The reliability of the test (instrument) can be
estimated by examining the consistency of the responses
between the two tests.
Alternative Form Method: this method also requires two
testing's with the same people. However, the same test is not
given. Each of the two tests must be designed to measure the
same thing and should not differ in any systematic way. One
way to help ensure this is to use random procedures to select
items for the different tests.
Prerequisites for Understanding Assessments
Split-Halves Method: This method is more practical in that it
does not require two administrations of the same or an
alternative form test.
In the split-halves method, the total number of items is
divided into halves, and a correlation taken between the two
halves.

6. Test Reliability is an important selling point for publishers of
standardized tests, especially in high-stakes testing. If an
institute asserts that its instrument can identify children who
qualify for a special education program, the users of that test
would hope that it has a high reliability. Otherwise, some
children requiring the special education may not be identified,
whereas others who do not require the special education may be
unnecessarily assigned to the special education program.
Prerequisites for Understanding Assessments
Minimum Standards for Reliability:
Test scores used for administrative purposes and reported for
groups of students; a reliability of .60 should be the minimum.
This low standard is acceptable because group means are not
affected by a tests lack of reliability
For weekly (or more frequent) testing used to monitor student
progress, a reliability of .70 should be the minimum. This
relativity low standard is acceptable because random
fluctuations can be taken into account when a behavior or skill
is measured often.
If a decision is being made is a screening decision (i.e., used as
a recommendation for further assessment) there needs to be
higher reliability. For screening purposes a standard of .80 is
recommended
If a test is used to make decisions for an individual student
(tracking, or special educational placement) the recommended
standard is .90

7. Prerequisites for Understanding Assessments
Measures of Dispersion:
Range: The difference between extremes of a distribution
Variance: description of the dispersion ofa set of scores around
the mean.
Standard Deviation: the positive square root of the variance.
Prerequisites for Understanding Assessments
Standard Error of Measurement
Prerequisites for Understanding Assessments
Prerequisites for Understanding Assessments
Summarizing Student Performance

8. 1. Percent correct
2. Accuracy
3. Instructional level
Frustration: (too difficult- the stduetn knows less than 85%
of the material
Instructional: material where the child is likely to be
successful , but success is not guaranteed (responses between
85-95% correct)
Independent: the student can perform without assistance more
than 95% accuracy)
Prerequisites for Understanding Assessments
Interpretation of Test Performance
There are 3 common ways to interpret an individual students
performance:
1. criterion referenced: given by teachers to establish how well
students have learned the data and skills that were taught in the
class.
Standards referenced (Standards Based Assessment, content
standards or curriculum frameworks), adopted by states and
districts that describe what students should know and be able to
do in different subjects at various grade levels.
They also have performance standards that define how much of
the content standards students should know to reach the "basic"
or "proficient" or "advanced" level in the subject area.

9. Prerequisites for Understanding Assessments
Norm referenced: a type of test, assessment, or evaluation
which yields an estimate of the position of the tested individual
in a predefined population, with respect to the trait being
measured.
Important Characteristics for Normed Assessments:
1. Gender 4. Race and Cultural Identity
2. Age 5. Geography
3. Grade on School 6. Intelligence
7. Acculturation of parents