Teaching Ratio and Proportion - Assignment Example

1. How does the research design control for the following threats* to internal validity:
a. Selection: Depending on the two classes chosen, the demographics of the school itself can greatly influence the outcome of the experiment due to goals. Both classes belonged to a small public secondary school. Depending on who the subjects are, the outcome could be seen as different.

b. Maturation: This could change during the experiment due to children getting older and more mature and therefore, can handle concepts more easily.
c. Mortality: The dropping out of subjects can lead to overall attrition but should not have an impact on the internal validity of the experiment. As long as the control group is consistent within the rest of the experiment, people dropping out only lessons the subject amount and not the quality of the subjects.
d. Regression: This has to do with aiming towards the average. The people with the lowest score aim to get a higher mark because they can only “get better”. Instead of looking at it from an “improvement” standpoint, it is essential to view the subjects as making gradual strides to improve instead of an obvious jump.

e. Testing: If you repeatedly test a student, this could easily lead to a bias that causes change within the experiment. Subjects may remember the correct answer from previous questions and therefore, they are not coming from an unbiased perspective but instead, using memory to help them get through. Also, sometimes too much testing does not give enough room for actual growth.

f. Instrumentation: Depending on what instruments or manipulatives are used during the experiment, the outcome can be different. The Partial experiment is different from the full experiment due to its implementations.
g. History: History can affect the outcome because students are affected every day by their environment and therefore, without the control of the variables, nothing is consistent. This can greatly affect the experiment as history changes perspective.
*If any of these threats are not a credible concern in the study, explain why.

2. What are the findings of the study (be brief)?
The findings of the study are that the pupils involved in the “full experiment” and the partial experiment scored differently due to exposure to manipulatives and instrumentation. The full investigation is more suited for the “educated” population rather than the 7th-grade norm population. The Partial Experiment was more prevalent in the regular 7th-grade population.
3. Is the study internally valid? Why or why not? The study is internally valid because it deals more with things that can be controlled such as selection, history, maturity, and instrumentation.
4. Is the study externally valid? Why or why not? This study has external validity because it includes pre-test and post-test, situation-specific observations, and it plays greatly off the independent variables. Read More