Chapter 15 validity of design Flashcards

1
Q

statistical conclusion validity

A

Is there an actual relationship between the I and D variables?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

statistical conclusion validity: statistical power

A

its ability to document a real relationship between I and D variables?
A study with low Power may not be able to establish this
-usually due to low sample size may not provide a statistical difference
-while a very large sample size may contribute to showing a statistical difference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

statistical conclusion validity: violated assumptions of statistical tests

A

the assumptions that exist, if not met, may lead to erroneous inferences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

statistical conclusion validity: reliability and Variance

A

statistical conclusions are messed up by certain things as unreliable measurement, failure to standardize the protocol, environmental interferences, or heterogeneity of subjects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

statistical conclusion validity: Failure to use Intention to Treat Analysis

A

when subjects go missing or do not finish the research, the ITT helps to control for this

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Internal Validity :

A

given a statistical relationship between the I and the D, is there evidence that one causes the other?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Internal Validity : T/F The assumption of causality or cause and effect require three components: temporal precedence, covariation of cause and effect, and no plausible alternative explanations.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Internal Validity: temporal precedence

A

the cause, precedes the effect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

internal validity: covariation of cause and effect

A

the outcome only occurs in the presense of the intervention

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Internal validity: no plausible alternative explanations

A

alternative explanations not plausible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Internal vs social threats

A

internal threats of validity of design are events of changes that occur during a study that may affect the relationship between the I and the D
Social threats of validity of design are the pressures that can occur in research that may lead to differences between groups
i.e. (performance bias where one group is aware of the other group)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Internal threats

A

history
Maturation
Attrition
Testing
Instrumentation
Regression to the Mean

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Internal Threats : History

A

Did unanticipated events occur during the study that could affect the dependent variable?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Safeguard for History

A

Random assignment
Time or plan the study better to avoid predictable event
Apply statistical adjustment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q
  • If participants were also involved in other activities or received
    other type of intervention (e.g., OT), this is an example of what type of internal threat?
A

it is an example of History
threat that interferes with the study Results

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Internal threat :Maturation

A

Were changes in the dependent variable due to normal development or the simple passage of time?
Child growing up, person getting older, spontaneous recovery post stroke

17
Q

Possible solution / safeguard for Maturation?

A
  • Use random assignment
  • Apply statistical adjustment
  • Randomize the testing or treatment order
18
Q

Internal threat : attrition / experimental mortality

A

Is there a differential loss of subjects across groups?
Studies with long follow ups are prone to Attrition.

19
Q

Safeguard for Attrition?

A
  • Replacement of lost subjects if possible
  • Re-examination of data to see existing status;
  • Statistical “intention-to-treat” (ITT) analysis
20
Q

Internal threat : testing

A

Did the pretest or repeated test affect scores on the posttest?
Repeated testing on subjects may lead to increased familiarity of inappropriate cues provided by the tester

21
Q

Solution or safeguard for TESTING?

A

o Elimination of multiple testing;
o Use of randomly selected experimental and
control groups;

22
Q

Internal threat : Instrumentation

A

Did the dependent variable change because of how it was measured?
Problems with the tool used to measure the variables of interest
Inappropriate selection of the tool

23
Q

Safeguard/solution to instrumentation?

A

o Select appropriate technique or instrument
o Calibrate instrument
o User training or practice in taking measurement

24
Q

Internal threat : Regression to the Mean

A

Is there evidence of regression from pretest to posttest
scores?
Occurs when subjects enter a study with an extreme value (outlier) for baseline of outcome measure

25
Q

Solution/safeguard for regression to the mean?

A

o To trim outliers;
o To take repeated baseline measures;
o To use a control group

26
Q

Internal threat: Assignment / selection

A

Is there bias in the way subjects have been assigned to experimental groups?
Unequal baseline characteristics of groups that might influence the study’s outcome.

27
Q

Possible solution/safeguard for assignment

A

o Random assignment to groups;
o Adequately defined inclusion and exclusion
criteria;
o Statistical adjustments e.g., analysis of
covariance (ANCOVA)

28
Q

AHA TIMS

A
  • Attrition
  • History
  • Assignment
  • Testing
  • Instrumentation
  • Maturation
  • Statistical regression to mean
29
Q

Ruling Out Threats to internal threats of the Internal
Validity

A

▪Random assignment (and control groups) may
control threats due to
✓history,
✓maturation,
✓Assignment/selection,
✓regression to the mean,
✓testing,
✓instrumentation

30
Q

Construct Validity

A

▪Construct validity, in the context of design, concerns how variables are conceptualized.
▪is concerned with the meaning of variables within a study, and whether the IV/DV are well-established and correctly labeled, specifically.
▪ often (but not exclusively) related to measure/test:
to compare the variables with their measures to
determine if the measure truly represents the variable, e.g.,
➢ shoulder function vs. active ROM

31
Q

Construct Validity

A

▪ Threats can occur regarding
* Operational definitions (OD)
* Time frame: length of a study
* Multiple treatment interactions: Tx, other than the one of interest, is
administered, e.g., Parkinson medication vs. deep brain stimulator (DBS)
* Experimental bias related to subjects/investigators (Refer to previous
module on blinding/masking as strategy)
✓ Subjects’ performance bias;
✓ Investigators’ bias toward a particular outcome

32
Q

“Hawthorne Effect”

A
  • One possible type of experimental bias
  • The effect of subjects’ knowledge that they are part of a
    study on their performance
    ➢ First described related to a series of experiments on workers’ performance
    ➢ However a number of flaws in the original experiments
33
Q

External Validity

A

▪is the extent to which the results of a study may be generalized to outside experimental situation, e.g., other individuals or
circumstances

34
Q

Threats to External Validity

A
  1. Biased sample selection (influence of selection) - only a narrowly defined subset of subjects/persons; - only woman not man or vice versa
  2. Setting differences (influence of setting)
    - environment of the study was different from what would be applied in clinic
  3. Time (influence of history)
    – considerably changed circumstances (e.g., updated practice guideline)
35
Q

Interesting point from book

A
  • As consumers of research evidence, we are responsible for making
    judgments about the degree of internal validity of a study, and the
    extent to which we consider findings relevant and useful.
  • When internal validity is severely threatened, conclusions can be
    considered suspect. We might assume that peer review would
    prevent publication of such studies, but that is not necessarily the
    case—caveat emptor!
36
Q

“Intention to treat (ITT)” (not Tx but statistical analysis)

A
  • ITT analysis is usually described as “once randomized, always analyzed”.
  • ITT analysis includes every subject who is randomized according to randomizedtreatment assignment.
  • It ignores noncompliance, protocol deviations,
    withdrawal, and anything that happens after randomization.
  • ITT analysis maintains baseline/prognostic balance
    generated from the original random allocation or
    assignment (see slide #9).
37
Q

Statistical Conclusion Validity

A

▪Appropriate use of statistical procedures to assess the
relationship between the independent and dependent variables (IV and DV)
▪ Potential threats
* Low statistical power (e.g., small sample size)
* Violated assumptions of statistical tests
✓ level of measurement, frequency distribution
* Reliability and variance (unreliable measure)
* Failure to use “intention to treat (ITT) analysis”

38
Q

Types of design validity

A

Statistical conclusion validity (relationship)
Internal validity (evidence for cause and effect / experimental )
Construct validity (what parts can be generalized)
External validity (can the results be further generalized, persons setting, or times)

39
Q

Step 3: Appraise the Literature

A

Three primary questions:
▪ Is the study valid?
▪ Are the results meaningful?
▪ Are the results relevant to my patient?