Internal and External Validity

**Plausible Rival Hypothesis**

Something that explain the outcome of our study/our findings other than the manipulated variables (extraneous variables)

**Four Types of Experimental Validity and Purpose**

Experimental validity: use to evaluate the methodology of a study

1) Internal Validity

2)External Validity

3) Construct Validity

4) Data-Evaluation/Statistical Conclusion Validity

Purpose: We can say we have a good study and provide strength and confidence of a study

**Internal Validity**

To what extent results are attributed to the effects of the IV instead of an extraneous variable (looking causal (cause and effect)  relationship b/w IV (intervention) and DV (outcome))

**External Validity**

To what extent the results can be generalized or extended to people, settings, times, measures/outcome other than those included in this particular demonstration

**Construct Validity**

Given that the intervention (IV) was responsible for change, what specific aspects of the manipulation was the mechanism, process or causal agent? What is the conceptual basis (construct) underlying the effect?

**Data-Evaluation Validity**

To what extent is a relation shown between the intervention (IV) and the outcome (DV)? What about the data and methods used for evaluation that could mislead or obscure demonstrating or failing to demonstrate an experimental effect?

**8 Threats to Internal Validity** 

* History
* Maturation
* Testing
* Instrumentation
* Statistical Regression
* Selection Biases
* Attrition
* Diffusion to Treatment

**History**

1. ==Any events that happen during the time of the study c==an could affect the performance of the subject


1. It influences the results
2. Example: an earthquake or blackout that occurs during the time of the study that affects the results 
3. Control of history: is to ensure a control group in your study and to be sure to do random assignment 

**Maturation**

1. ==Change occurring within the individual== during the time if the study


1. Time can often lead to change 
2. Example: Factors that affect subject’s performance because of the passing of time such as hunger, tiredness, physical growth
3. Control of Maturation: A control group

**Testing**

1. Pre-test/Post-test
2. Testing repeated ==will give the subject familiarity/practice with the measure/test==


1. Influencing the outcome of the 2nd test
3. Control: administering the DV once or Solomon Four-Group Design


1. 1st group is measured pre and post, gets the intervention in between
2. 2nd group is measured pre and post, but gets no intervention
3. 3rd group is measured post only, and gets the intervention
4. 4th group is measure post only and does not get intervention

Instrumentation

1. Contextual change of experiment; when researchers is the measure and may give different scoring over time 


1. Test might remain the same, but the ==context in which it is administered could differ==
2. Example: judges in the olympics or judges giving parole  
3. Control of Maturation: A control group
4. ==Response Shift==


1. Changes that happens when a subject’s standards for rating own functioning shifts over time

Statistical Regression