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Statistics > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

What is the most rigorous form of scientific investigation for testing hypotheses

A

Experiment

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2
Q

What is the purpose of an experiment

A

to support a cause and effect relationship between a particular action or condition (independent variable) and and observed response (dependent variable)

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3
Q

What is an extraneous variable

A

any factor that is not directly related to the purpose of the study, but that may affect the dependent variable

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4
Q

What is it called when extraneous variables are not controlled for and contaminate the independent variable in such a way that their separate effects are obscured

A

Confounding influence

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5
Q

What are the three essential characteristics a study must have in order to be considered a true experiment

A
  1. The independent variable must be manipulated by the experimenter
  2. The subjects must be randomly assigned to groups
  3. A control or comparison group must be incorporated within the design
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6
Q

What are the two types of independent variables

A

Active and Attribute

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7
Q

What is an active independent variable

A

It is one that is manipulated by the experimenter so that the subjects are assigned to levels of the independent variable

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8
Q

What is an attribute independent variable

A

It is a variable that the researcher is not able to assign; Must observe within natural groupings according to inherent characteristics. ie: Age, gender, occupation

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9
Q

What does random assignment mean

A

each subject has an equal chance of being assigned to any group

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10
Q

What is the most effective design strategy for ruling out extraneous effects

A

The use of a control group against which the experimental group is compared

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11
Q

When is it justifiable to design studies with comparative treatments as controls

A

When previous research has clearly established their effectiveness against a true control group, or when it is considered unreasonable to leave patients untreated

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12
Q

What type of analysis eliminates subjects who did not get or complete their assigned treatment, and include only those subjects who sufficiently complied with the trials protocol

A

On- Protocol or On-treatment analysis

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13
Q

How might bias effect the results of an on-protocol analysis

A

It will favor the treatment, as those who succeed at treatment are the most likely to stick with it

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14
Q

What is Intention to Treat Analysis

A

When data are analyzed according to the original random assignments, regardless of the treatment subjects actually received. Analyze the data in the way we INTENDED to treat the subjects

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15
Q

Do most researchers use On-Protocol or Intention to Treat Analysis

A

Most researchers analyze data using both just to be safe

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16
Q

What is the Noncompleter equals failure approach for handling missing data

A

When the outcome is dichotomous, dropping out is considered failure. Patients who refused their assigned intervention, who received additional, or who were missing final measurements are also considered failures.

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17
Q

What is the most conservative approach for handling missing data

A

Noncompleter equals failure

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18
Q

What is the Last Observation Carried Forward approach for handling missing data

A

the subjects last data point before dropping out is carried forward and used as the outcome score

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19
Q

What is a double blind study

A

Neither the subjects nor the investigator are aware of the identity of the treatment groups until after data are collected

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20
Q

What kind of bias does blinding guard against

A

Observation bias

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21
Q

When would a single blind study be appropriate

A

When it is not possible or feasible to blind the subjects from which group they are a part of; only the measurement team is blinded

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22
Q

What is the simplest way to control for specific subject traits that may interfere with the dependent variable

A

Choosing subjects who are homogeneous

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23
Q

What is one of the major drawbacks of homogeneous subjects in an experiment

A

Research findings can be generalized only to the type of subjects who participated in the study

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24
Q

To control for extraneous effects, you can systematically manipulate attribute variables and build them into the experimental design as an independent variable. When this is done, what is that new independent variable referred to as

A

Blocking variable

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25
Q

What would you be controlling for if you use a matching procedure to guarantee an equivalent group of males and females within different age ranges in the experimental and control groups

A

Extraneous variables

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26
Q

When the levels of the independent variable are assigned to different groups, the variable is considered what

A

an independent factor

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27
Q

When all levels of the independent variable are experienced by all subjects, the independent variable is considered what

A

a repeated factor or repeated measure

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28
Q

What type of design ensures the highest possible degree of equivalence across treatment conditions because the subjects are matched with themselves

A

a repeated measures designs

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29
Q

What statistical technique is used to equate groups on extraneous variables; making covariates artificially equivalent across groups

A

Analysis of Covariance (ANCOVA)

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30
Q

What is a covariate

A

an identified extraneous variable; can be controlled for using ANCOVA

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31
Q

What are the 5 design strategies for controlling intersubject differences

A
  1. Selection of homogeneous subjects
  2. Blocking
  3. Matching
  4. Using subjects as their own controls
  5. Analysis of covariance
32
Q

What is statistical conclusion validity

A

concerns the appropriate use of statistical procedures; if inappropriate, may lead to invalid conclusions about the relationship between independent and dependent variables

33
Q

What are the threats to statistical conclusion design validity

A
  • Low Statistical Power
  • Violated assumptions of statistical tests
  • Error rate
  • Reliability
  • Variance
34
Q

What is internal validity

A

focuses on the cause and effect relationship; Given a statistical relationship between the independent variable and dependent variable, is there evidence that one causes the other

35
Q

What three components are required for the assumption of causality

A
  1. Temporal Precedence
  2. Covariation of cause and effect
  3. No plausible alternative explanations
36
Q

What types of threats to internal validity exist

A
  • Single group threats
  • Multiple group threats
  • Social threats
37
Q

What are the six types of single group threats to internal validity

A
  1. History
  2. Maturation
  3. Attrition
  4. Testing
  5. Instrumentation
  6. Regression toward the mean
38
Q

What are the four types of social threats to internal validity

A
  1. Diffusion or imitation of treatment
  2. Compensatory equalization of treatment
  3. Compensatory Rivalry
  4. Resentful demoralization
39
Q

What are the five threats to construct validity of causes and effects

A
  1. Operational Definitions of independent and dependent variables
  2. Time frame within operational definitions
  3. Multiple treatment interactions
  4. Experimental bias
  5. Hawthorne effect
40
Q

What are the three threats to external validity

A
  1. Interaction of treatment and selection
  2. Interaction of treatment and setting
  3. Interaction of treatment and history
41
Q

What is temporal precedence

A

documenting that the cause precedes the effect; change in outcome must be observed only after a treatment is applied

42
Q

What is covariation of cause and effect

A

Showing that the outcome only occurs in the presence of the intervention or that the degree of outcome is related to the magnitude of the intervention

43
Q

What is meant when we say there is no plausible alternative explanations to a result in an experiment

A

Helps us explain a cause and effect relationship and increase internal validity. States that there are no competing explanations for the result, such as confounding variables which may have caused the result.

44
Q

What is meant by single group threats to internal validity

A

threats that may affect the relationship between the independent and dependent variables when only one group of subjects is tested

45
Q

Explain the single group threat: History

A

refers to the confounding effect of specific events, other than the experimental treatment, that occur after the introduction of the independent variable or between a pretest and posttest. ie: if studying exercise plan on knee extensor strength, subjects participation in additional exercise would be a history threat

46
Q

Explain the single group threat: Maturation

A

concerns processes that occur simply as a function of time and are independent of external events. May cause subjects to respond differently on a second measurement because they have grown older, stronger, healthier, more experienced, etc since the first measurement

47
Q

Explain the single group threat: Attrition

A

When a study drops out of a study before it is completed. Concerning when it results in a differential loss of subjects, dropouts that occur for specific reasons related to the experimental situation

48
Q

Explain the single group threat: Testing

A

concerns the potential effect of pretesting or repeated testing on the dependent variable. The mere act of collecting data could change the response that is being measured. Increased skill may occur because of familiarity with the measurements.

49
Q

What are reactive measurements

A

Tests that have the potential to change the response they are measuring. Occur when testing process stimulates change rather than measuring passive behavior. Someone being taped might change their behavior because they know they are being watched

50
Q

Explain the single group threat: Instrumentation

A

concerned with the reliability of the measurement. ie: Changes that occur because of calibration of measuring tool, measuring therapist becomes better at measurement over the course of the research study

51
Q

Explain the single group threat: Regression toward the mean

A

Even in the absence of intervention, extreme scores on the pretest tend to regress toward the mean on the posttest

52
Q

How are multiple group threats similar to single group threats

A

Explain similar threats to validity, but concern the relationship between independent and dependent variables when more than one group is being tested

53
Q

Explain the multiple group threat: Selection interaction

A

refers to factors other than the experimental intervention that can influence posttest differences between groups. When groups are not comparable, the single group threats to internal validity may affect the groups differently

54
Q

Explain the multiple group threat: Selection- History Effects

A

result when experimental groups have different experiences between pretest and posttest, especially important in multicenter studies

55
Q

Explain the multiple group threat: Selection - Maturation

A

Occur when the groups experience maturational changes at different rates, ie: if studying motor development in kids ages 3 and 10, we can expect a different rate of change that could confound treatment affects

56
Q

Explain the multiple group threat: Selection- Testing

A

Occurs when the pretest affects each group differently

57
Q

Explain the multiple group threat: Selection - Instrumentation

A

occurs when the test is not consistent across groups, often due to variances in reliability

58
Q

Explain the multiple group threat: Selection- regression

A

of concern if the groups are specifically divided based on higher and lower pretest scores

59
Q

Explain what is meant by a social threat to internal validity

A

refer to the pressures that can occur in research situations that may lead to differences between groups

60
Q

Explain the social threat: Diffusion or imitation of treatments

A

Because the nature of many interventions makes blinding impractical, control subjects are often aware of the interventions intended for another group, and may attempt to change their behaviors accordingly

61
Q

Explain the social threat: Compensatory equalization of treatments

A

When an experimental treatment is considered a desirable service or condition, those who work with and care for the subjects might try to even out experiences by providing compensatory services to the control group

62
Q

Explain the social threat: Compensatory Rivalry

A

When one groups assigned treatment is perceived as more desirable than the others, subjects receiving the less desirable treatment may try to compensate by working extra hard to achieve similar results

63
Q

Explain the social threat: Resentful Demoralization

A

When one groups assigned treatment is perceived as more desirable than the others, subjects receiving less desirable treatment may be demoralized and resentful, Their reaction may be to respond at lower levels of performance

64
Q

What are Constructs

A

abstract behaviors that cannot be directly observed, but that can be inferred from other relevant observable variables

65
Q

What is Construct validity of causes and effects

A

Concerns the theoretical concepts of the intervention and response variables, and whether these have been developed sufficiently

66
Q

Explain how the operational definition related to an experiment can affect construct validity

A

When studies incorporate only one type of measurement or only one age group is measured, we can generalize outcomes only to events similar to measurements or age groups tested

67
Q

Describe how construct validity might be affected by multiple treatment interaction

A

If multiple treatments are given, it is difficult to generalize effects of treatment. Limited by the possibility of carryover or combined effects; cannot generalize to situation where only one treatment is given

68
Q

Describe how construct validity might be affected by order effects

A

can result when treatments or measurements are consistently given in the same order, creating possible influences on subsequent responses; cannot generalize where only one treatment is given or given in different order

69
Q

Describe how construct validity may be affected by length of follow up

A

If a study addresses the response of subjects over time, cannot generalize result outside of that time frame. ie: basing long term decisions on short term data

70
Q

Describe how experimental bias can affect construct validity

A

Concern biases that are introduced into a study by expectations either of the subject or the experimenter. Subject might try their best/ try harder because they want to meet the expectations of the experimenter, this no longer represents natural behavior

71
Q

What is the Hawthorne effect? How can it affect Construct Validity

A

It is the tendency of persons who are singled out for special attention to perform better merely because they are being observed. No longer natural behavior, cannot generalize

72
Q

Describe how experimenter effects may affect construct validity

A

Experimenters may have certain expectations that influence how subjects respond, may react more positively to subjects in the experimental group or give less attention to the control group

73
Q

What is external validity

A

refers to the extent to which the results of a study can be generalized beyond the study sample; can the results be generalized to persons, settings, and times from those in the experimental situation?

74
Q

Describe how interaction of treatment and selection can affect internal validity

A

If subjects are sampled according to specific characteristics, those characteristics define the target population and results cannot be generalized to those who do not have these characteristics

75
Q

Describe how interaction of treatment and setting can affect external validity

A

If we find a causal relationship between an exercise program and functional improvement in a rehabilitation hospital, can we generalize these findings to a nursing home or home care; Have to replicate these results in different settings.

76
Q

Describe how interaction of treatment and history can affect external validity

A

Concerns the ability to generalize results to different periods of time in the past of future.

77
Q

What is the CONSORT statement

A

Guidelines for reporting that help authors and readers determine why a study was undertaken and how it was conducted and analyzed. It is composed of a checklist of 22 items pertaining to the content of the Title, Abstract, Introduction, methods, results, and discussion sections of an article.

Statistics (7 decks)

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