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66 Cards in this Set
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Case Control study
 compares what groups?  asks "what......?" 
 with DISEASE vs. without DISEASE
 "What HAPPENED?" 

Case Control study
 measures what? 
 Odds Ratio (OR)


Cohort study
 compares what groups?  asks "what ......?" 
 w/ RISK FACTOR vs. w/o RISK FACTOR
 "What WILL HAPPEN?" 

Cohort study
 measures what? 
 Relative Risk (RR)


Cross Sectional Study
 asks "what .......?" 
 "What ...IS HAPPENING?"


Cross Sectional Study
 measures what? 
Disease Prevalence
(Dz freq. & related risk factors) 

Cross Sectional study
 can show what?  but does NOT show what? 
 Risk Factor association with Dz
 does NOT Establish Causality 

Twin Concordance Study
 compares what data?  compares btw what groups? 
 Frequency of Dz (prevalence)
 monozygotic twins & dizygotic twins 

Adoption Study
 compares what data?  compares btw what groups? 
 Frequency of Dz (prevalence)
 Siblings raised by biologic vs. adoptive parents 

Twin Concordance study measures?
Adoption study measures? 
 Heritability
 Heritability & Environmental Factors 

Clinical Trials Phase I
 Sample size  Type of patients  Purpose 
 Small number of patients
 Healthy volunteers  Pharmacokinetics (safety & toxicity) 

Clinical Trials Phase II
 Sample size  Type of patients  Purpose 
 Small number of patients
 Pts with Disease of interest  Pharmacodynamics (efficacy & dosing & side effects) 

Clinical Trials Phase III
 Sample size  Type of patients  Purpose 
 Large number of patients
 Pts with Disease of interest randomly assigned to either New Tx or to best available Tx (or placebo)  Compares new Tx to current standard of care 

Highest echelon of clinical evidence occurs with what type of study?
How is this study performed? 
MetaAnalysis
 pools data from several studies to achieve overall conclusion 

Sensitivity & Specificity Table

Sensitivity & Specificity Table


Ratio Calculation Table

Ratio Calculation Table


Hypothesis Table

Hypothesis Table


Sensitivity = ?

= TP / (TP + FN)


Specificity = ?

= TN / (TN + FP)


Sensitivity > 1 is desirable to rule _____ disease?
Specificity > 1 is desirable to rule _____ disease? 
 Out
(indicates low FP rate)  In (indicates low FN rate) 

Sensitivity = 1  ?
Specificity = 1  ? 
 False Negative rate
 False Positive rate 

If 100% sensitivity, then all negatives must be?

 True Negatives
(FN = 0) 

If 100% specificity, then all positives must be?

 True Positives
(FP = 0) 

Sensitivity is used as a screening tool in what type of diseases?

 diseases with Low Prevalence


Positive Predictive Value (PPV) = ?

= TP / (TP + FP)


Negative Predictive Value (NPV) = ?

= TN / (TN + FN)


Sensitivity measures _______ of people who ______.
PPV measures _______ of test results that are ______. 
 Proportion
 Test Positive  Probability  TP 

A, B, & C indicates?

A = 100% sensitive
B = Most ACCURATE C = 100% specific 

Under what conditions would a High Sensitivity or Specificity provide a Low PPV?

 if the Prevalence is Low


Odds ratio = ?

= (a/d) / (b/c)
(or .... = ac / bd) 

Relative risk = ?

= [a / (a+b)] / [c / (c+d)]


Attributable risk = ?

= [a / (a+b)]  [c / (c+d)]


H0 is what?
H1 is what? 
 Null hypothesis
 Alternate hypothesis 

Null hypothesis implies what association?

No association btw Dz & Risk factor


Alternate Hypothesis (H1) implies what association?

 Association exists btw Dz & Risk Factor


Alpha & Beta is what type of error?

Type I error
Type II error 

Type I error (Alpha) occurs when a study shows what?

Effect (or difference) Exists
when in reality None Exists ("convicting an innocent man") 

Type II error (Beta) occurs when a study shows what?

No Effect (or difference) Exists
when in reality, it Exists ("setting a guilty man free") 

In assessing errors, what is ... p?

 probability of making a Type I error


In assessing errors, what does it mean when p < 0.05?

 less than 5% chance that
data will show something that is NOT really there 

Mistakingly accepting Experimental hypothesis (H1), while rejecting Null hypothesis (H0) is called?

 Type I error


Mistakingly accepting Null Hypothesis (H0), when in reality the Experimental Hypothesis (H1) is false is called?

 Type II error


Power is defined as the probability of?

 rejecting Null hypothesis (H0)
when it is false (likelihood of finding a difference that exists) 

Equation
 Power = ? 
= 1  B


Percentage within
 1 standard deviation  2 standard deviation  3 standard deviation 
 68.0 %
 95.0 %  99.7 % 

Equation
 Standard Error of Mean (SEM) = 
= SD / (sqrt of n)
(SD = Standard Deviation) (n = sample size) 

As SAMPLE SIZE (n) increases,
 Standard Error of Mean (SEM) will?  compare SEM to SD 
 decrease
 less than SD 

CONFIDENCE INTERVAL (CI)
 is the range btw? 
[mean  Z(SEM)]
to [mean + Z(SEM)] 

95% Confidence Interval implies what:
 p value?  Z value? 
p = 0.05
Z = 1.96 

Define ........ t  test

Difference btw the MEANS of 2 groups
("Mr. T is Mean") 

Define ....... ANOVA test

Difference btw the MEANS of 3+ groups
(ANalysis Of VAriance of 3+ variables) 

ChiSquared (X^2)
 compares? 
2 or more proportions (or percentages)
(or categorical outcomes, not means) 

Correlation Coefficient (r)
 if value is closer to 1, it implies what? 
 stronger correlation btw 2 variables


Equation
 Coefficient of Determination = ? 
= r^2


BMI
 equation 
= [(weight in kg) / (height in meters)^2]


BMI
 normal values  obese values  morbidly obese values 
Normal: 18.5 to 24.9
Obese: > 30.0 Morbidly Obese: > 40.0 

Type of Skew & Implies what?

Positive Skew
(Positively RIGHT on the Tail) Mean > Median > Mode 

Type of Skew & Implies what?

Negative Skew
Mean < Median < Mode (Left Tail...Means Less) 

What variable is affected LEAST by Outliers?

 Mode


Random Error
 implies test study has REDUCED value of what? 
(REP SAV)
 Reduced PRECISION 

Systemic Error
 implies test study has REDUCED value of what? 
(REP SAV)
 Reduced ACCURACY 

Precision implies what occurence in test measurements?
Precision implies the absence of what in test measurements? 
 Consistency & Reproducibility
(Reliability)  Random Variation 

Accuracy implies what occurence in test measurements?

 Trueness
(Validity) 

Picture depicts what?

Left = Accuracy (reliability)
Right = Precision (validity) 

H0 is NOT rejected, if the 95% CI for:
 MEAN difference btw 2 variables ..... 
 includes 0


H0 is NOT rejected, if the 95% CI for:
 OR or RR ........ 
 includes 1
