Internal Validity When considering the internal validity, we are considering how

Question

Internal Validity

When considering the internal validity, we are considering how confident we are in a conclusion of "Changes in Variable X cause a change in Variable Y"

We evaluate if we actually started with two equal groups (selection effect). And we evaluate if we only changed the independent variable (testing effect, history effect, maturation effect, mortality effect). Finally, we ask if we ruled out all possible confounds.

PART 1:

Frances did a study to investigate the effect of concreteness on memory. She created a list of 120 items that are very concrete (such as pencil and table) and a list of 120 items that are very abstract (such as justice and freedom). She decided to use the 300 students in her Research Methods class as participants. In class one day, she projected the 120 concrete words for one second each. Then asked the participants to write down as many as they could remember. Later in that class period, she projected the 120 abstract words for one second each and asked the participants to write down as many as they could remember. What is the biggest threat to internal validity?

SELECT ONE OF THE FOLLOWING:

A. mortality / attrition effect
B. maturation effect
C. selection effect
D. history effect

PART 2:

Confounds are variables that provide an alternate explanation because they change along with the independent variable. That is, one level of the independent variable is always associated with one level of the confounding variable. In this example, identify a confounding variable:

1.
    Dr. Cross has changed a requirement in PSC041. She wants to know if this change improves student learning. She compares the test scores from the first midterm this quarter to the test scores from the first midterm last quarter. It turns out that the students this quarter scored higher on that test. She concludes that the changed requirement facilitates student learning.

SELECT ONE OF THE FOLLOWING:

A. Quarter
B. Instructor
C. course requirements
D. midterm one

2.

There are many approaches to treating psychiatric disorders. Training to become a therapist requires choosing which approach you want to learn. A study of therapy effectiveness on substance abuse had the experimental group undergo therapy with a psychodynamic approach administered by Dr. Elektra, while the other group participated in therapy with a cognitive approach administered by Dr. Ponder. Each participant attended a total of twenty 1-hour sessions.

SELECT ONE OF THE FOLLOWING:

A. duration
B. substance abuse status
C. therapist
D. therapeutic approach

PART 3:

You ask your high school teachers to estimate your intelligence (they have a really good idea of how intelligent you are!) Your teachers rate your intelligence as 135 (genius!). You then take an IQ test three times. Here are the results:

Trial one: 100 (average)
Trial two: 58 (not able to tie your own shoe laces)
Trial three: 143 (genius)

This IQ test is:

SELECT ONE OF THE FOLLOWING:

A. neither reliable nor valid
B. reliable and valid
C. reliable but not valid
D. not reliable but valid

Explanation / Answer

1) Mortality/Attrition effect

2.2) Instructor

2.2)substance abuse status

3). not reliable but valid because standard deviation is high

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