Chapter 9: Internal Validity
Activity 9.1: Threats to Internal Validity
Activity 9.2: What Type of Threat?
Activity 9.3: Controlling Threats to Internal Validity
Threats to Internal Validity
Which threat to internal validity exists in each of the situations listed below?
Column A: Situation Column B: Threat to Internal Validity
1. A researcher wishes to compare a. Maturation
changes in achievement motivation of b. Mortality
males and females during their high c. Data collector characteristics
school years. During her study, she d. Location
discovers that more males than females e. Instrumentation
failed to complete high school. f. Regression
2. Two groups of students are compared
with regard to their attitude toward a
career in the military. Two different
recruiting officers administer the same
attitude scale to each group. The
recruiter who administers the scale to
the first group is in uniform; the second
recruiter is in civilian clothes.
3. Those students who score in the top 2
percent on a biology test have, on
average, lower scores the second time
they take the test.
4. A researcher wants to measure changes
in student attitudes toward their
graduate programs at a local university.
He finds a questionnaire used by
another researcher the previous year
that asks most of the questions he wants
to ask. To improve it, he changes some
of the questions and adds a few more.
5. A researcher observes level of attention
in a special program during the month
of September and again in May.
6. A researcher interviews two groups of
individuals. One group is interviewed
in his classroom; the other group,
although asked the same questions, is
interviewed in the student union.
What Type of Threat?
Match the letter of the appropriate research methodology from Column B with its topic in
Column A: Examples Column B: Type of Threat
1. ______ The scorers of an examination a. Subject characteristics
unconsciously grade the exam papers
in such a way that some students b. History
receive lower scores than they deserve.
2. ______ The taking of a pretest by
students participating in a research d. Attitude of subjects
study allows them to figure out the
nature of this study. e. Mortality
3. ______ Two existing groups are f. Data collector bias
compared with respect to their scores
on an achievement test. g. Testing
4. ______ A fire drill occurs during the h. Instrument decay
taking of a final examination. Several
students complain they did not have
enough time to complete the exam.
5. ______ Change during an intervention
is due to just the passing of time rather
than the intervention itself.
6. ______ The way in which students are
ask to participate in a study affects
how they perform.
Controlling Threats to Internal Validity
Suggest a way to control each of the following threats to internal validity.
1. Instrument decay ______________________________________________________
2. Subject characteristics __________________________________________________
3. Loss of subjects (mortality) ______________________________________________
4. Data collector characteristics _____________________________________________
5. Location _____________________________________________________________
6. Regression ___________________________________________________________
7. Implementation _______________________________________________________
8. Attitude of subjects ____________________________________________________
Problem Sheet 9: Internal Validity
1. Place an X after any of the threats listed below that you think might apply to your
Subject characteristics ______ Instrumentation______ Maturation___________
Mortality______Testing ________ History_________Subject attitude________
2. Please describe how you will attempt to control for those threats that you have
3. What assurances can you provide (through your design, sampling procedures, etc.)
to support the claims that your study findings are valid? In other words how wil you
convince the reader that the findings or relationships resulting from the study are
not due to or explained by something other than what you claim?