Stats - clinical trials and validity

Question 1

What is the purpose of the Phase 1 trial?
How many people are involved?

Answer 1

Phase I clinical trials involve only a small number of healthy people (possibly as few as 15-20). The focus is to evaluate the drugs safety, determine a safe dosage range, and identify side effects.

Question 2

What is the purpose of the Phase 2 trial?
How many people are involved?

Answer 2

In Phase II clinical trials the drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety

Question 3

What is the purpose of the Phase 3 trial?
How many people are involved?

Answer 3

In phase III trials the drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments (or placebos), and collect information that will allow the experimental drug or treatment to be used safely.

Question 4

What is the purpose of the Phase 4 trial?

Answer 4

Phase IV trials (aka Post Marketing trials) are done after the drug has been granted a license. They gather further information on the drug in areas not addressed in the previous trials (e.g. Safety in pregnancy) and also to find other potential uses for the drug.

Question 5

Validity refers to the extent to which something measures what it claims to measure. The first major distinction is between internal and external validity.

What is internal validity?

Answer 5

Internal validity is the confidence that we can place in the cause and effect relationship in a study. It is the confidence that we have that the change in the independent variable caused the observed change in the dependent variable (rather than due to poor control of extraneous variables)

Question 6

Validity refers to the extent to which something measures what it claims to measure. The first major distinction is between internal and external validity.

What is external validity?

Answer 6

External validity is the degree to which the conclusions in a study would hold for other persons in other places and at other times, i.e. its ability to generalise

Question 7

What is the difference between validity and reliability?

Answer 7

Validity refers to the extent to which something measures what it claims to measure.

Reliability is the extent to which an experiment, test, or any measuring procedure yields the same result on repeated trials.

Question 8

What are the threats to internal validity?

Question 9

What are the threats to external validity?

Question 10

What type of validity is this?

This refers to the general impression of a test. A test has this validity if it appears to test what it is meant to

Answer 10

Face validity

Question 11

What type of validity is this?

This refers to the extent to which a test or measure assesses the full content of a subject or area. For example if a test is designed to help diagnose depression, it would have poor [X-type] validity if it only asked about psychological symptoms and neglected biological ones

Answer 11

Content validity

Question 12

What type of validity is this?

This oncerns the comparison of tests. You may wish to compare a new test to see if it works as well as an old, accepted method. The correlation coefficient is used to test such comparisons

Answer 12

Criterion validity

Question 13

What type of validity is this? (Sub category)

The predictor and criterion data are collected at or about the same time. An example could be testing a new, shorter test of intellectual functioning against a standard measure

Answer 13

Criterion (concurrent)

Question 14

What type of validity is this? (Sub category)

In this validation, the predictor scores are collected first and criterion data are collected at some later/future point. Here you want to know if the test predicts future outcomes. An example might be evaluating a new assessment method to select medical students. The test could be compared against the students performance at the end of year one to see if there is a correlation

Answer 14

Criterion (predictive)

Question 15

What type of validity is this? (Sub category)

A test has this validity if it has a high correlation with another test that measures the same construct
i.e. the degree to which a test / measure is similar to other test / measures that it theoretically should be similar to

Answer 15

Construct (convergent)

Question 16

What type of validity is this? (Sub category)

This is demonstrated through a low correlation with a test that measures a different construct
i.e. the degree to which a test / measure is not similar to other test / measures that it theoretically should be not be similar to

Answer 16

Construct (divergent)

Question 17

What are the 2 subtypes of
1) criterion validity
2) construct validity

Answer 17

1) concurrent and predictive
2) convergent and divergent

Question 18

What type of validity is this?

The extent to which a test measures the construct it aims to

Answer 18

Construct