Trick or Threat
Internal and External Validity
Mirna Henriquez & Faith Oketch
Threats to Internal and External Validity
Music Background
Threats to Internal Validity
- History
- Maturation
- Testing Effects
- Ceiling effects
- Floor effects
- Instrumentation effects
- Selection bias
- Statistical regression
- Mortality (attrition)
- Teacher effects
- School effects
- Class effects
History
Maturation
Testing effects
Ceiling effects
Floor effects
Instrumentation effects
Selection bias
Statistical regression
Mortality (attrition)
Teacher effects
School effects
Class effects
Threats to External Validity
- Lack of internal validity
- Nonrepresentativeness
- Artificiality
- Reactivity
- Hawthorne effect
- John Henry effect
Lack of internal validity
Nonrepresentativeness
Artificiality
Reactivity
Hawthorne effect
John Henry effect
Activity: Name and explain the example of the scenario.
Activity: Name and explain the example of the scenario.
1. An elementary school teacher finds that her first grade students are having trouble with their basic mathematics concepts. She therefore tries a new teaching method and plans to evaluate it at the end of the year to see if it has made an improvement. She will consider her program successful if the children have mastered a large number of skills at the end of the year which they had not mastered at the beginning of the year. Which of the following is the most obvious threat to the evaluation of the program?
2. Each year an elementary school teacher provides a lesson in his physical education class on ‘The Rules of International Soccer (Football).’ In 2010, since it was a Soccer World Cup year, he decided to revise and upgrade the lesson. He initiated his lesson to coincide with the start of the televised portions of the World Cup. In the final exam, he asked his usual ten questions about International soccer. He found that the 2010 students scored substantially higher than the students from the previous three years had on the same questions. He concluded that his new program had been effective. Which of the following is the most obvious threat to the internal validity of the study?
3. Wilma's parents and teacher were concerned about her noncompliance, so they consulted a behavior therapist. They all decided together that the first order of business was to gauge the extent of the problem. For the next week, her teacher recorded all instances of the target behavior at school and her parents recorded all instances at home. Noncompliance was defined a failure to respond to an instruction within 10 seconds. The resultant data indicated that, when asked to do something, Wilma was four times more likely to obey the instruction at home than at school. They concluded that the problem was considerably worse at school, and consequently they decided to employ a different behavioral procedure in each setting.