A pretest-posttest design is an experiment in which measurements are taken on individuals both before and after they’re involved in some treatment.
Pretest-posttest designs can be used in both experimental and quasi-experimental research and may or may not include control groups. The process for each research approach is as follows:
Quasi-Experimental Research
1. Administer a pre-test to a group of individuals and record their scores.
2. Administer some treatment designed to change the score of individuals.
3. Administer a post-test to the same group of individuals and record their scores.
4. Analyze the difference between pre-test and post-test scores.
Example: All students in a certain class take a pre-test. The teacher then uses a certain teaching technique for one week and administers a post-test of similar difficulty. She then analyzes the differences between the pre-test and post-test scores to see if the teaching technique had a significant effect on scores.
Experimental Research
1. Randomly assign individuals to a treatment group or control group.
2. Administer the same pre-test to all individuals and record their scores.
3. Administer some treatment procedure to individuals in the treatment group and administer some standard procedure to individuals in the control group.
4. Administer the same post-test to individuals in both groups.
5. Analyze the difference between pre-test and post-test scores between the treatment group and control group.
Example: A teacher splits randomly assigns half of her class to a control group and the other half to a treatment group. She then uses a standard teaching technique and a new teaching technique with each group respectively for one week and then administers a post-test of similar difficulty to all students. She then analyzes the differences between the pre-test and post-test scores to see if the teaching technique had a significant effect on scores between the two groups.
Potential Issues with Internal Validity
Internal validity refers to the extent in which a study establishes a reliable cause-and-effect relationship between a treatment and an outcome.
In a pretest-posttest design experiment, there are several factors that could affect internal validity, including:
- History – Individuals experience some event outside of the study that affects the measurements before and after a treatment.
- Maturity – Biological changes in participants affect the measurements before and after a treatment.
- Attrition – An individual leaves the study before a post-measurement can be taken.
- Regression to the mean – People who score extremely high or low on some measurement have a tendency to score closer to the average next time, despite the treatment they partake in.
- Selection bias – The individuals in the treatment group and control group are not actually comparable.
Often random selection and random assignment of individuals to groups can minimize these threats to internal validity, but not in all cases.
Additional Resources
The following tutorials provide additional information about different types of experimental designs:
Split-Plot Design: Definition & Example
Matched Pairs Design: Definition & Example
Cross-Lagged Panel Design: Definition & Example
For an experimental design, the researcher can make cause-and-effect inferences and this type of research is useful for determining whether or not a specific counseling intervention is effective. This session will provide an introduction to the basics underlying experimental design, such as reliability, validity, and replicability.
Topic Outcomes:
By the end of this session, students will be able to:
Examine the principles of experimental research in counseling.
Consider models of experimental design.
Evaluate threats to internal and external validity.
Explore applications of experimental research in counseling contexts.
Good day, how do we calculate the resultes?
Thanks Zach!
I’m still having trouble deciding which level of measure to use with my pretest/posttest design. I am using the test for two purposes: pretest/posttest compare control /treatment student scores & comparing teacher effective instruction using students score outcomes as a factor. Am I using interval or ratio?
Hello Zach!
My research is about the effectiveness of a program I designed. I will have 2 groups: experimental and control randomly selected, and participants were randomly selected before that. I will give the pretest to the 2 groups, then teach the programme to the experimental group only (i.e. . the control group will receive no treatment) & finally give the post test to both groups. Am I on the right track?
Khadija
Hello sir good evening, presently I am about to craft a pre and post-test to evaluate the students’ knowledge before the training. the problem is where do i begin and what is the format for these tests? thank you very much.
Hi Eduardo…To begin crafting a pre-test and post-test for evaluating students’ knowledge before and after training, follow these steps:
### 1. **Identify Learning Objectives:**
– Clearly define the key knowledge or skills that the training aims to impart.
– Each test question should align with these objectives to ensure the test accurately measures the intended outcomes.
### 2. **Designing the Test Format:**
– **Multiple-Choice Questions (MCQs):** These are commonly used for assessing knowledge. Ensure each question has one correct answer and plausible distractors.
– **Short Answer/Essay Questions:** Useful for assessing deeper understanding or the ability to articulate knowledge.
– **True/False Questions:** Good for assessing basic understanding of key concepts.
– **Matching Items:** Can be used to assess knowledge of relationships between concepts.
– **Practical/Application-Based Questions:** For training that involves skills, you can include scenarios or problems that require application of the knowledge.
### 3. **Crafting the Pre-Test:**
– **Purpose:** To assess the students’ baseline knowledge.
– **Question Difficulty:** Questions should range from basic to more challenging to gauge the full spectrum of student understanding.
– **Content:** Focus on the core concepts that will be covered in the training. Avoid including content that hasn’t been introduced yet.
### 4. **Crafting the Post-Test:**
– **Purpose:** To measure what the students have learned during the training.
– **Question Parity:** Ideally, the post-test should mirror the pre-test in format and content, but with different questions that assess the same concepts.
– **Include Higher-Order Thinking Questions:** If applicable, include questions that require students to analyze, evaluate, or create based on the knowledge they’ve gained.
### 5. **Scoring and Analysis:**
– **Consistency:** Ensure the scoring method is consistent between pre and post-tests.
– **Comparison:** Analyze the difference between pre-test and post-test scores to assess the effectiveness of the training.
– **Feedback:** Provide feedback to students on both tests to reinforce learning.
### 6. **Pilot Testing:**
– Before administering the tests to the full group, consider piloting them with a small group to identify any issues with question clarity or difficulty.
### 7. **Implementation:**
– Administer the pre-test before any instruction begins.
– After the training, administer the post-test under similar conditions to ensure comparability.
### Example Format:
– **Pre-Test:**
– 10 multiple-choice questions covering the basics of the training content.
– 2 short-answer questions to assess prior understanding.
– **Post-Test:**
– 10 multiple-choice questions that mirror the pre-test but with different phrasing or context.
– 1 scenario-based question that requires application of the knowledge gained.
This structured approach will help you create effective pre and post-tests that accurately measure the impact of your training.
Please i need a response on this👇
In a quasi-experimental study where students are treated for 4 weeks on a topic they have not been previously taught before post test to compare the performance of students in the experimental and control groups. Should the same instrument be used for pre and post test in view of the fact that the test is constructed on what they are taught during the 4-week experiment? Should I use related background concepts for the pretest to establish equivalence or otherwise?
Hi Nweke…While we cannot recommend guidance on your study, we can clarify any concepts from the tutorial itself.