Exam 2 Flashcards
The less precise a measurement is, the lower association between:
that variable and any other variable
What can effect whether or not the strength of a relationship is underestimated?
Imprecision
A strong association may be found if a measure is:
Reliable and Fairly Precise
What must you consider when interpreting and applying the results of research into the association between variables?
Whether the sample studied truly represents the range of the population of interest
Generalization of results into practice is a judgment of the clinician, but the investigator must provide sufficient description
***What is the fundamental statistic for the analysis of interval and ratio data to estimate the strength of the association between variables?
Regression Analysis
***What is a special case of regression?
ANOVA
***What is the simplest form of regression?
Simple Linear
***What is used to measure the strength of the association between pairs of data that are interval or ratio?
Pearson r Value
***What can you use to estimate the association between multiple variables? And what test is better suited for this?
Multiple Regression; ANOVA
What is the value of a multiple regression test?
R2 Value
What does R2 measure?
The variance in the criterion variable (Y) explained by a predictor variable (X) or predictor variables
What is the difference between normal values for R and R2?
r: (-1 to 1)
R2: (0 to 1)
What value is indicative that the differences observed when studying a sample are reflective of true population differences?
P-Value
***What are the guidelines for interpreting r values?
Little, if any correlation: .00 to .25; 00 to -.25
Low Correlation: .26 to .49; -.26 to -.49
Moderate Correlation: .50 to .69; -.50 to -.69
High Correlation: .70 to .89; -.70 to .89
Very High Correlation: .90 to 1.0; -.90 to 1.0
What do Measures of Association not imply?
Cause and Effect
Although measures of association confirm cause and effect, these analyses can build useful what?
Predictive Models
What analysis method is used most often for Ordinal Data?
Spearman Rank Order Correlation “Spearman r” (e.g. Likert Scale)
What is the formula for a Spearman Rank Order Correlation?
r = 1 – ((6∑d2) / n(n2 – 1))
What is the most common approach for Nominal Data?
Cramer’s V Correlation “Chi Square”
What is one example of a Spearman r analysis?
Likert Scale
What is one example of a Chi Square analysis?
Testing the hypothesis that two nominal variables are independent
What can a Cramer’s V analysis identify?
A relationship, but it may have no suggestion of cause and effect
Are Spearman r and Cramer’s V parametric or nonparametric statistics?
Nonparametric
Are parametric or nonparametric statistics more powerful? Why?
Parametric, nonparametric uses less information in its calculation
What scales belongs to which type of statistics?
Nominal and Ordinal are nonparametric
Interval and Ratio are parametric
What type of data will you get with a Pearson r test?
Interval or Ratio
Generalization of results into a clinical practice is a judgment of who, and requires thoughtful decisions on the part of whom?
The clinician; the investigator
Estimating the usefulness of any diagnostic procedure involves comparing the results of a diagnostic test to the results of what?
“Gold” standard
What reasons would a gold standard test not be applied to all diagnoses in question?
Setting, timing, scope, costs, and risks associated with the diagnostic process
The results from studies of diagnostic tests are reported in what forms?
Estimates of Sensitivity and Specificity
Positive and Negative Prediction Values
Positive and Negative Likelihood Ratios
Receiver Operator Characteristic Curves
When comparing the results from a diagnostic test with a dichotomous result of interest to the results of a “gold standard” diagnostic test, how many subgroups will be formed?
4
Sensitivity and Specificity are related to the ability of a test to identify what?
Those with and without a condition
What is sensitivity?
The number of illnesses of injuries that are correctly diagnosed by the clinical examination procedure being investigated (A) divided by the true number of illnesses/injuries (A + C)(Gold standard measure)
What is the sensitivity formula?
A/A+C
What is specificity?
The number of individuals correctly classified as not having the condition based on the test being investigated (D) divided by the true number of negative cases (B+D)(Gold standard measure)
What is specificity formula?
D/D+B
Tests that have a high sensitivity are at what?
Ruling out a condition
Have relatively few false negative findings
Tests that have a high specificity are good at what?
Ruling in a condition
Have few false positive findings
Do tests with high specificity have few or many false positives?
Few
What is the formula for Positive Prediction Values?
A/A+B
What is the formula for Negative Prediction Value?
D/D+C
What is the correlation between prevalence, PPV, and NPV?
As prevalence falls, PPV falls and NPV rises
What are values derived from estimates of sensitivity and specificity?
Likelihood Ratios
Knowledge of the Likelihood Ratio influences ________ that a condition does or does not exist at the end of the examination
The Level of Certainty
What sort of ratio is an impact of a positive examination finding on the probability that the target condition exists?
Positive Likelihood Ratio
What is the formula for a Positive Likelihood Ratio?
Sensitivity/(1 - Specificity)
How do you interpret Positive Likelihood Ratios?
A Large +LR Rules In a disorder
What sort of ratio is an impact of a negative examination on the probability that the condition in question is present?
Negative Likelihood Ratio
What is the formula for Negative Likelihood Ratios?
(1 - Sensitivity)/Specificity
How do you interpret a Negative Likelihood Ratio?
A Large -NR Rules Out a disorder
How do you interpret Likelihood Ratios?
LR > 1: Indicates probability that the target/problem/disease is present; +LR
LR < 1: Indicates a decreased probability that the target/problem/disease is present; -LR
LR = 1: No change in the probability
What is the full LR Table?
> 10: Large and often conclusive increase in the likelihood of disease
5 - 10: Moderate increase in the likelihood of disease
2 - 5: Small increase in the likelihood of disease
1 - 2: Minimal increase in the likelihood of disease
1: No change in the likelihood of disease
0.5 - 1.0: Minimal decrease in the likelihood of disease
0.2 - 0.5: Small decrease in the likelihood of disease
0.1 - 0.2: Moderate decrease in the likelihood of disease
< 0.1: Large and often conclusive decrease in the likelihood of disease
What is the Pretest Odds Ratio formula?
Pretest Probability/ (1 - Pretest Probability)
What is the Posttest Odds Ratio formula?
Pretest Odds * LR
What is the formula for Posttest Probability?
Posttest Odds/ (Posttest odds + 1)
What is the purpose of an ROC Curve?
It is helpful for determining a cut-off score for deciding things like the number of positive special tests are required to determine a diagnosis
How can you tell if a test discriminates between the presence or absence of a disorder?
It examines the trade off between sensitivity and specificity when you select different cut-off values
What are the interpretations of an ROC Curve?
A truly useless test has an area of 0.5 (it is no better than flipping a coin)
A perfect test has an area of 1.00 (a test with 0 false positives or false negatives)
What are the ROC score breakdowns?
.9 - 1.0: Excellent .8 - .9: Good .7 - .8: Fair .6 - .7: Poor .5 - .6: Fail
Which point, that gives a balance between sensitivity and specificity of a test, should be used as a cutoff in an ROC curve?
The point where the curve “turns”
What does STARD stand for?
Standards for the Reporting of Diagnostic Accuracy Studies
How many aspects are looked into for the STARD?
25
What is the framework of risk identification and injury prevention?
- Establishing the extent of the injury problem (Incidence, Severity)
- Establishing etiology and mechanism of sports injuries
- Introducing a preventative measure
- Assessing its effectiveness by repeating step 1
What is the importance of Establishing the extent of the injury problem?
Done through prospective injury surveillance and anecdotal observations
What is the importance of Establishing the etiology and mechanisms of the sports-related injuries?
The cause of a sports injury may be traumatic or atraumatic
Identifying the mechanism of injury: observational research
Identifying risk factors that may be involved in the etiology of a specific injury: collection of baseline data to assess potential risk factors followed by a prolonged period of injury surveillance
What is the importance of Introducing a preventative measure?
The intervention should be based on information gained in the first two steps of the paradigm
Avoid the use of the “shotgun approach” of injury prevention
What is the importance of Reassessing the extent of the injury problem?
If the incidence and severity of injuries have been substantially reduced, the permanent implementation of the intervention is likely warranted
What kind of design is the gold standard for studies of injury risk factors?
Prospective Cohort Design
How does a Prospective Cohort Designed study work?
A large of participants potentially “at risk” for injury of interest are baseline tested. Participants are followed over time to determine if they go on to suffer the injury