6 Approaches to Diagnostic Assessment

Six Approaches to Diagnostic Assessment

Approach 1: Profiling Content Strengths and Weaknesses

In this approach, a deficit is defined as a student’s low standing, relative to peers, in a broad learning outcome area in a subject.  

Example: A student may have less ability in subtraction and division than in addition and multiplication compared to peers.

A student with a “weakness” is significantly below the norm – Percentile ranks are the primary type of norm-reference score used in this context.

• Strengths: This approach to diagnostic assessment is most useful to give you a general idea about students’ performance in subareas of a subject matter.
• Weaknesses: If the set of items that a test has to indicate performance on a particular standard contains only a handful of items or tasks, the subtest scores probably will be unreliable.  This approach does not tell you about attainment of particular learning goals in the absolute sense; rather, it gives relative strengths and weaknesses within the group.

Approach 2: Identifying Prerequisite Deficits

In this approach, a deficit is defined as a student’s failure to have learned concepts and skills necessary to profit from instruction in a course or a unit.  

• Select one learning objective the student must be able to perform.
• Analyze it to identify the prerequisites a student must learn in order to achieve it.

• For each prerequisite identified, repeat the same analysis, generating a hierarchy of prerequisite performances.

• Once you have created the hierarchy, assess each student with several items of each of the prerequisites identified.

The difference between this approach and the previous one is that here you focus on whether each prerequisite was learned rather than on the pattern of profile strengths and weaknesses.

• Strengths: This approach very specifically identifies skills that students need to learn before they are ready to be taught new learning targets.  
• Weaknesses: This approach is limited by the care and accuracy with which you analyze the learning requirements of your curriculum.  If you do not identify the proper prerequisites, your assessment will lack validity.

Approach 3: Identifying Objectives Not Mastered

In this approach, a deficit is defined as a student’s failure to master one of more end-of-instruction learning objectives.  The differences between this approach and the identifying prerequisite deficits approach is that here you assess only the objectives that are the outcomes of the unit or the course, not the prerequisite objectives.  

• For each teaching unity, identify and write statements of the learning objectives that are the main outcomes of the unit or course.
• For each learning objective, design four to eight test items.
• Revise the items as necessary to obtain a closer match.
• Assemble the items into a single assessment instrument if the list of learning objectives is relatively short (less than six) – otherwise, depending on the students’ educational development, you may need to divide the assessment into two or more instruments.
• For ease of scoring, keep all the items that assess the same objective together in one assessment.

Set a “mastery” or passing score for each learning target – a frequently used passing score is 80%.  

• Strengths: Diagnostic assessments based on specific objectives are appealing because they (a) focus on specific and limited learning targets to teach, (b) communicate learning targets in an easy-to-understand form, and (c) focus your attention on students’ observed performance.
• Weaknesses: Objectives-based diagnostic assessments are generally plagued with measurement error, primarily because the assessments tend to have too few items per objective.  The results give you little information about how to remediate the deficits you discover.  

Approach 4: Identifying Students’ Errors

In this approach, a deficit is defined as the type(s) of errors a student makes.  The goal is to identify student errors, rather than making a simple mastery-nonmastery decision about overall performance on a particular objective.  

Examples: Failure to regroup when “borrowing” in subtraction, improper punctuation of vowels when reading, revising i and e when spelling, and producing a sentence fragment when writing.