As an educator, ensuring the quality and effectiveness of your assessments is crucial. One key aspect of assessment validity is content validity – the degree to which your test or evaluation instrument accurately measures the specific knowledge, skills, and abilities it claims to assess.
Let’s explore the concept of content validity and provide a step-by-step guide for evaluating the content validity of your own assessments.
Content Validity Examples
Content validity ensures your assessment matches the intended learning objectives and curriculum. Here are a few examples that illustrate the concept:
Example: Math Exam for 5th Graders
A 5th-grade math exam should primarily assess students’ understanding of the mathematical concepts, skills, and problem-solving abilities outlined in the 5th-grade math curriculum, such as operations with whole numbers, fractions, decimals, measurement, and basic geometry. Including questions about advanced algebra or calculus concepts would lack content validity, as they do not align with the expected learning outcomes for that grade level.
Construct vs. Content Validity in Educational Assessments
Construct validity and content validity are related but distinct concepts that are crucial to consider when developing and evaluating educational assessments.
Construct validity refers to the degree to which an assessment measures the specific knowledge, skills, or abilities it is intended to evaluate. If an exam intended to measure mathematical reasoning abilities also includes irrelevant items on vocabulary or spatial reasoning, it would have compromised construct validity, as it is not purely assessing the target construct.
To establish strong construct validity, assessment developers must demonstrate both:
- Convergent Validity: The test scores correlate with performance on other measures of the same construct, such as classroom grades or performance-based tasks.
- Discriminant (Divergent) Validity: The test scores show little to no correlation with measures of unrelated constructs, such as musical aptitude or physical fitness.
Note: In contrast, content validity focuses on ensuring the assessment comprehensively covers the relevant content domain. For an exam designed to evaluate student mastery of 8th-grade science standards, content validity would require that the test questions collectively address the full range of disciplinary core ideas, science and engineering practices, and crosscutting concepts outlined in the standards.
Example: Content Validity in a Biology Assessment
Imagine a biology exam to measure students’ understanding of key concepts in cellular biology. A test with high content validity would include topics such as cell structure and function, cellular processes like photosynthesis and respiration, and the role of organelles. However, if the exam predominantly focused on genetics and evolution while omitting fundamental cellular biology concepts, it would lack sufficient content validity.
In this case, even if the exam demonstrated strong construct validity in measuring some aspect of biological knowledge, it would not comprehensively evaluate the intended cellular biology construct. Ensuring content validity is essential for creating assessments that meaningfully capture the full scope of the targeted learning objectives.
Step-by-Step Guide: Evaluating Content Validity for a Survey
Ensuring strong content validity is crucial when developing survey instruments to collect reliable data. Following a systematic process, you can rigorously evaluate how much a survey comprehensively captures the intended constructs. Here’s a step-by-step guide:
Step 1: Assemble a Panel of Subject Matter Experts
Measuring content validity requires input from a panel of deeply knowledgeable individuals about the constructs being assessed through the survey. This may include researchers, practitioners, or other experts in the relevant domain.
Step 2: Have Experts Rate Each Survey Item
Provide the expert panel with the survey instrument and instructions to rate each question or item based on its relevance to the target constructs. Typically, a 3-point scale is used, where experts classify each item as “essential,” “useful but not essential,” or “not necessary.”
Step 3: Calculate the Content Validity Ratio (CVR)
For each survey item, calculate the Content Validity Ratio (CVR) using the formula:
CVR = (ne – N/2) / (N/2)
Where:
ne = number of experts rating the item as “essential”
N = total number of experts on the panel
The CVR ranges from -1 to +1, with higher values indicating greater content validity.
Example: Calculating the Content Validity Ratio
Suppose you have a panel of 10 SMEs evaluating a questionnaire. For a particular question, 8 SMEs rated it as “essential.”
Given:
- Number of SMEs (N) = 10
- Number of SMEs rating the item as “essential” (n_e) = 8
Plugging these values into the CVR formula:
CVR = (n_e – N/2) / (N/2)
CVR = (8 – 10/2) / (10/2)
CVR = (8 – 5) / 5
CVR = 3 / 5
CVR = 0.6
The CVR for this question is 0.6, indicating that most SMEs (more than half) considered it essential for the questionnaire.
Step 4: Calculate the Content Validity Index (CVI)
Calculate the Content Validity Index (CVI) by averaging the CVR values for all items to obtain an overall measure of content validity for the full survey instrument.
CVI = Sum of all CVR values / Total number of items
A CVI of 0.80 or higher indicates acceptable content validity.
Let’s say you have a survey with 10 items, and you have calculated the Content Validity Ratio (CVR) for each item based on the ratings provided by a panel of subject matter experts (SMEs). The CVR values for the 10 items are as follows:
| Item | CVR |
| 1 | 0.8 |
| 2 | 0.6 |
| 3 | 0.9 |
| 4 | 0.7 |
| 5 | 0.8 |
| 6 | 0.5 |
| 7 | 0.9 |
| 8 | 0.6 |
| 9 | 0.8 |
| 10 | 0.7 |
To calculate the Content Validity Index (CVI), you need to sum up all the CVR values and divide by the total number of items:
CVI = Sum of all CVR values / Total number of items
CVI = (0.8 + 0.6 + 0.9 + 0.7 + 0.8 + 0.5 + 0.9 + 0.6 + 0.8 + 0.7) / 10
CVI = 7.3 / 10
CVI = 0.73
In this example, the CVI for the survey instrument is 0.73. Since the commonly accepted threshold for an acceptable CVI is 0.80 or higher, this survey instrument falls slightly below the recommended level of content validity.
If the CVI is below 0.80, consider reviewing the items with lower CVR values (e.g., items 2, 6, and 8) and either revise them or remove them from the survey. After making the necessary changes, you can recalculate the CVR for the modified items and determine the updated CVI to ensure that the survey instrument meets the acceptable content validity threshold.
Note: As a student, you may not have access to a panel of subject matter experts. In such cases, it is possible to use a panel of your peers instead. Just be sure to acknowledge this limitation when reporting.