Chapter 10

Question 1

What is a clinical trial

Answer 1

an experimental study that examines the effect of interventions on patient or community populations

Question 2

What is the difference between a therapeutic trial and a preventive trial

Answer 2

• A therapeutic trial examines the effect of a treatment or intervention on a particular disease
• A Preventive trial evaluates whether a procedure or agent reduces the risk of developing the disease

Question 3

What is a between subjects design

Answer 3

Subjects are assigned to independent groups using a randomization procedure

Question 4

What is a randomized block design

Answer 4

Subjects are first classified according to an attribute (blocking variable) and then randomized into treatment groups

Question 5

What is a within subjects design (repeated measures)

Answer 5

A design in which subjects act as their own control

Question 6

What is a pretest- posttest control group design

Answer 6

Used to compare two or more groups that are formed by random assignment. One group receives the experimental variable and the other acts as the control. Both groups are tested prior to and following treatment with the only difference between them being what happens between the measurements

Question 7

What is a treatment arm of a study

Answer 7

The independent groups in a design. ie: the experimental group and the control group are each a treatment arm. If the study contained two experimental groups and one control, there would be 3 treatment arms

Question 8

What is a two group pretest- posttest design

Answer 8

This design incorporates two experimental groups formed by random assignment without a “true control”. This is performed with a control condition is not feasible or ethical, often comparing a “new” treatment with an “old”.

Question 9

What is a multi group pretest- posttest control group design

Answer 9

Like a pretest- posttest, compares a control group with an experimental group, but allows researchers to compare several treatment and control conditions. For instance 2 experimental groups and one control group.

Question 10

How are pretest-posttest designs analyzed with Numeric Data

Answer 10

Change Scores; represent the difference between the posttest and pretest

Question 11

How are pretest-posttest designs analyzed with Interval and Ratio Data

Answer 11

Difference scores are compared using an unpaired t test or if three or more groups, a one way analysis of variance (ANOVA)

Question 12

How are pretest-posttest designs analyzed with Ordinal Data

Answer 12

Two groups: Mann Whitney U

Three or More: Kruskal-Wallis ANOVA

Question 13

What is a posttest only control group design and when would you use it

Answer 13

Used to compare two or more groups that are formed by random assignment. One group receives the experimental variable and the other acts as the control. The groups are tested following treatment only, no pretest is performed. Used when a pretest is either impractical or potentially reactive

Question 14

How are posttest only designs analyzed with Interval and Ratio Data

Answer 14

Two groups: unpaired t test

More than two groups: One way ANOVA

Question 15

How are posttest only designs analyzed with Ordinal data

Answer 15

Two groups: Mann Whitney U

Question 16

What is a factorial design

Answer 16

Incorporates two or more independent variables. Described according to their number of factors. Can also be described by number of levels within each factor. ie: 2x4 design includes two variables with 2 and 4 levels respectively

Question 17

What is a two way factorial design

Answer 17

Incorporates two independent variables

Question 18

What does it mean when independent variables are said to be “completely crossed” in a design

Answer 18

every level of one factor is represented at every level of the other factor and that each group represents a unique combination of the levels of these variables

Question 19

What is the difference between the main effect and the interaction effect

Answer 19

In multifactorial studies, the main effect is concerned with examining each independent variable with scores collapsed across the other independent variable. Interaction effect is concerned with how one independent variable interacts with the other.

Question 20

What is the purpose of using a randomized block design

Answer 20

When the investigator is concerned that an extraneous factor might influence differences between groups, one way to control for this is to build the variable into the design. Often an attribute variable such as gender. ie: To what degree does strength increase with an exercise program, may be different between the sexes, build this additional “blocking” variable into the design.

Question 21

What analysis should be performed on a randomized block design

Answer 21

can be analyzed using a two way ANOVA, Multiple Regression, or Discriminant Analysis

Question 22

What are some disadvantages of the repeated measures (within subjects) design

Answer 22

• potential for practice effects: the learning effect that can take place when one individual performs the same task over and over
• potential for carryover effects: when one subject is exposed to multiple treatment conditions

Question 23

How can you limit the effects of Carryover in within subjects designs

Answer 23

By allotting sufficient time between successive treatment conditions to allow for complete dissipation of previous effects

Question 24

When can a repeated measures (within subjects) design be considered “experiments”

Answer 24

When they incorporate randomization in the order of application of repeated conditions, and the comparison of one condition or intervention to another within one subject

Question 25

Describe a one way repeated measures (within subjects) design

Answer 25

Involves a single factor experiment where one group of subjects is exposed to all levels of one independent variable

Question 26

Describe how order effects should be considered when considering a repeated measures (within subjects) design

Answer 26

Because subjects are exposed to multiple treatment conditions in a repeated measures design, there must be a concern for potentially biasing effect of test sequence; This can be fixed by randomizing the order of presentation for each subject

Question 27

What is a Latin Square

Answer 27

A matrix composed of equal numbers of rows and columns, designating permutations of sequence combinations; Used to decrease order effects in a repeated measures design

Question 28

What data analysis should be performed on One way repeated measures designs

Answer 28

One Way ANOVA

Question 29

Describe a crossover design

Answer 29

In a repeated measures design, when only two levels of an independent variable are repeated, a preferred method to control for order effects is to counterbalance the treatment conditions so that their order is systematically varied. In a crossover design, half the subjects receive treatment A and then B and half receive B then A. Two subgroups are created, one for each sequence, and subjects are randomly assigned to one of the sequences

Question 30

When is the only time a crossover design should be used

Answer 30

Only in trials where a patients condition or disease will not change appreciably over time; not a reasonable approach when treatment effects are slow; especially useful when treatment conditions are immediately reversible

Question 31

If a treatment in a crossover design has some cumulative effect, what is essential to allow for a common baseline for each treatment condition

Answer 31

A Washout period

Question 32

What data analysis should be done for crossover designs

Answer 32

A paired t test can be used to compare change scores, or a two way ANOVA with two repeated measures can be used to compare pretest and posttest measures across both treatment conditions. The Wilcoxon signed ranks test should be used to look at change scores when ordinal data are used.

Question 33

Describe a two way design with two repeated measures

Answer 33

Repeated measures studies involving more than one independent variable. Can be expanded to include three independent variables

Question 34

What data analysis should be performed on two way repeated measures design

Answer 34

Two way ANOVA with two repeated measures is used to analyze differences across main effects and interaction effects

Question 35

Describe a mixed design

Answer 35

When a study incorporates two independent variables, one repeated across all subjects, and the other randomized into independent groups

Question 36

In a mixed design, what does it mean to have an independent factor and a repeated factor

Answer 36

- The variable whose levels have been randomly assigned is the independent factor - The variable that is repeated and all subjects are exposed to all levels is the repeated factor

Question 37

What data analysis should be performed on a two way design with one repeated factor

Answer 37

- Two way ANOVA is used to analyze main effects and interaction effects

Question 38

What is a sequential clinical trial

Answer 38

A special approach to the randomized clinical trial. Allows for continuous analysis of data as they become available, instead of waiting until the end to compare data. Results are accumulated as each subject is tested so that the experiment can be stopped as soon as the evidence is strong enough to determine a significant difference between treatments

Question 39

In a sequential clinical trial, what is meant by preference between groups

Answer 39

Specific criteria is set beforehand as a decision making factor for when to stop the experiment. Once this criteria is met, we can say that one group is "preferred" over the other

Question 40

What is a sequential chart

Answer 40

For each outcome or measurement in the study, the result is charted as being favorable toward one group or the other group. It is set up in a certain way so that with enough favorable results for one study, the "boundary" in the chart is crossed and a terminal decision is made that that group is considered to be preferable to the other group.

Question 41

What are the stopping rules when using a sequential chart

Answer 41

1. If upper boundary is crossed, a terminal decision is made and we can recommend A 2. If lower boundary is crossed, a terminal decision is made and we can recommend B 3. If the middle boundary is crossed, there is no preference

Question 42

What is the difference between a conditional decision and a terminal decision is a sequential trial

Answer 42

- Terminal decision is made when a boundary in the sequential chart is crossed - Conditional decision is rendered without crossing a boundary, but is based on practical considerations and observation of the plotted path.

Question 43

What is the difference between Efficacy and Effectiveness

Answer 43

- Efficacy is defined as the benefit of an intervention as compared to a control or standard program, provides information about the behavior or clinical variables under controlled, randomized conditions - Effectiveness refers to the benefits and use of the procedure under "real world" conditions