threats to internal validity

Quantitative research question: What are the advantages of reverse inclusion setting compared to full inclusion setting for preschoolers with disabilities based on their meeting their outcomes of annual goals and objectives?

I have taken each threat to internal validity and explained how each one may affect the quantitative research question stated above.

History would affect the study because of any unplanned event that would happen at school. The study would have to take place in a school setting based on the comparing of the two different settings of reverse inclusion to full inclusion classrooms. This would include events like fire drills, snow days, and other events that would cause the school to shut down.

Selection would affect the study because the participants in the study are young preschoolers and the sampling of the participants would depend on the parents’ willingness and consent for them to participate. Also with that said it would be very hard to get a good sampling of participates with the same background and characteristics.

Maturation would affect the study because of the setting being a place for intervention. Early childhood special education is to help students with developmental disabilities or other disabilities to receive intervention to help in areas they are deficient in. The study is actually looking at if they are able to accomplish these achievements in a specific setting more then another setting.

Pretesting would have an affect on this study because the students would not be tested in any way. Data would be taken of their goals and objects to see how they have made progress, then again to see any changes that may take place through out the period of the study.

Instrumentation would affect this study by having different people being observers in the classrooms. It would be more reliable if you could have one person be the observer in all participating settings. A way to help instrumentation would be to possibly video tape each participant in the settings. This way one person could be the observer and rater. They could also be using the same instrument to rate each participate in the settings.


Treatment replication would affect the study because of the participants being in different schools, and settings. Their teachers and teaching methods may not be same. Different interventions or different strategies would happen depending on how the teachers or therapist or the response of the individual student.

I would hope subject attrition would not affect this study but it is a possibility. Participates can move from area to another. Participates may also achieve their goals and objects, and may no longer need the special education services. Since this study is looking at students with disabilities who would meet the requirements to receive services, they would need to be receiving early childhood special education services in either of the settings being looked at. Because the participants are young, the parents could also decide to pull them out of the study.

Statistical regression may affect the study if the participants in the study are not making any progress on their goals and objects in their specific study. If there is no progress or the participant digresses in their abilities rather than making improvements there is a statistical regression.

The diffusion of treatment would affect the study possibly if the settings were possibly in the same school. Because of how uncommon a reverse inclusion classroom is, having the settings in the same school not be likely. If the settings were in the same school the teachers may be collaborating together. If the teachers are working collaboratively then they may be using the same intervention strategies in their classrooms.

Experimenter effect of the study may include the observer possibly being the teacher, who is documenting the data of students with a disability. Because the study is focused on trying to find the benefits of reverse inclusion, a teacher who is for reverse inclusion may be bias for that specific setting.

Because this study is on preschoolers, if a person were to come in to observer the classroom or a specific student, the student (participant) may either perform better then what they would normally do or they may perform worst then what they would normally do. This is called subject effects; the behavior of the student is changing because of just being in the study. A way to have this not affect the study is if the participant is video tape without their knowledge. The parents of the preschooler would be made aware of the video taping but the student would not be. This would help capture the true behaviors of the student in the specific setting.