BEHAVIORAL SCIENCE- Epidemiology/Biostatistics Flashcards
1
Q
Types of studies
A
Cross sectional study Case control study Cohort study Twin concordance study Adoption study
2
Q
Which kind of study is Cross sectional study?
A
Observational
3
Q
Collects data from a group of people to asses frequency of disease (and related risk factors) at a particular point in time
A
Cross sectional study
4
Q
What does Cross sectional study ask?
A
What is happening?
5
Q
What does Cross sectional study measure?
A
Disease prevalence
6
Q
Can show risk factor association with disease, but doesn’t establish casuality
A
Cross sectional study
7
Q
Which kind of study is Case control study?
A
Observational and retrospective
8
Q
Compares a group of people with disease to a group without disease
A
Case control study
9
Q
What does Case control study look for?
A
Look for prior exposure or risk factor
10
Q
What does Case control study ask?
A
What happened?
11
Q
This type of study measures Odds ratio (OR)
A
Case control study
12
Q
An example of this study is “Patients with COPD had higher odds of a history of smoking than those without COPD had”
A
Case control study
13
Q
What type of study is Cohort study?
A
Observational prospective or retrospective
14
Q
Compares a group with a given exposure or risk factor to a group without such exposure
A
Cohort study
15
Q
What does Cohort study look for?
A
Looks to see if exposure increases the likelihood of disease
16
Q
If Cohort study is prospective, what does it ask?
A
Who will develop disease?
17
Q
If Cohort study is retrospective, what does it ask?
A
Who devellop the disease? (exposed vs nonexposed)
18
Q
What is measure by Cohort study?
A
Relative risk
19
Q
It’s an example of which study: “Smokers had a higher risk of developing COPD than non smokers had”
A
Cohort study
20
Q
Compares the frequency with which both monozygotic twins or both dyzigotic twins develop same disease
A
Twin concordance study
21
Q
What does Twin concordance study measure?
A
Heritability and influence of enviromental factors (“nature vs nurture”)
22
Q
Compares siblings raised by biological vs adoptive parents
A
Adoption study
23
Q
What does Adoption study measure?
A
Heritability and influence of enviromental factors
24
Q
Experimental study involving humans
A
Clinical trial
25
Compares therapeutic benefits of 2 or more treatments, or of treatment and placebo
Clinical trial
26
When does the study quality of a Clinical trial improve?
When study is randomized, controlled, and double-blinded
27
What is a double blinded Clinical trial?
Neither patinet nor doctor knows wheter the patient is in the treatment or control group
28
What is a triple blind Clinical trial?
Refers to additional blinding of the researches analyzing the data
29
In which people is Phase I drug trial done?
Small number of healthy volunteers
30
What is the purpose of Phase I drug?
Assesses safety, toxicitym and pharmacokinetics
31
What does Phase I drug look for?
Is it safe?
32
In which patients is Phase II drug trial done?
Small number of patients with disease of interest
33
What does Phase II drug look for?
Does it work?
34
What is the purpose of Phase II drug?
Assesses treatment efficacy, optimal dosing, and adverse effects
35
In which patients is Phase III drug trial done?
Large number of patients randomly assigned either to the treatment under investigation or to the best available treatment (or placebo)
36
What does Phase III drug look for?
Is it as good or better?
37
What is the purpose of Phase III drug?
Compares the new treatment to the current standard of care
38
In which patients is Phase IV drug trial done?
Postmarketing surveillance trial of patients after approval
39
What does Phase IV drug look for?
Can it stay?
40
What is the purpose of Phase IV drug?
Detects rare or long term adverse effects
41
What can Phase IV drug result?
In a drug being withdrawn from market
42
What do Evaluation of diagnostic tests use?
Use 2 x 2 table comparing test results with the actual presence of disease
43
Which are the parameters taken in Evaluation of diagnostic test?
```
TP= True positive
FP= False positive
FN= False negative
FP= False negative
```
44
What does Evaluation of diagnostic test determine?
Sensitivity and specificity are mixed properties of a test (vs PPV and NPV)
45
What does Sensitive evaluates?
True positive rate
46
Proportion of all people with disease who test positive, or the probability that a test detects disease when disease is present
Sensitivity
47
What is the purpose of Sensitivity?
Value approaching 100% is desirable for ruling out disease and indicates a low false negative rate
48
What is the importance of high Sensitivity?
High sensitiity test used for screening in disease with low prevalance
49
Formula to determine Sensitivity
= TP/ (TP+FN)
| = 1 - false negative fate
50
What does Specificity evaluate?
True negative rate
51
Proportion of all people without disease who test negative, or the probability that a test indicates non-disease when disease is absent
Specificity
52
What is the purpose of Specificity?
Value approaching 100% is desirable for ruling in disease and indicates a low false positive rate
53
What is the importance of high Specificity?
= TN/ (TN+ FP)
| =1 - false positve rate
54
Proportion of positive test results that are true positive
Positive predictive value
55
What is the purpose of Positive predictive value?
Probability that actually has a the disease given a positive test result
56
Formula for Positive predictive value
= TP/ (TP+FP)
57
How does Positive predictive value varies?
Varies directly with prevalence or pretest probability: high pretest probability → high PPV
58
Proportion of negative test results that are true negative
Negative predictive value
59
What is the purpose of Negative predictive value?
Probability that a person actually is disease free given a negative test result
60
Formula for Negative predictive value
= TN / (TN+FN)
61
How does Negative predictive value varies?
Varies inversely with prevalence or pretest probability: high pretest probability → low NPV
62
Formula to determine Incidence rate
of new cases in a specified time period
Incidence rate= ----------------------------------------------------------
Population at risk during same time period
63
What does Incidence determine?
Looks at new cases
64
Formula of Prevalence
of existing cases
Prevalence = -------------------------------
Population at risk
65
What does Prevalence determines?
Looks at all current cases
66
How else is prevalence determine?
Prevalence = (Incidence Rate) x (Average Duration of Disease)
67
Types of Quantifyng risk
```
Odds ratio
Relative risk
Relative risk reduction
Attributable risk
Absolute risk reduction
```
68
When is Odds ratio typically used?
In case control studies
69
What is the purpose of Odds ratio?
Odds that the group with the disease (cases ) was exposed to a risk factor (a/c) divided by the odds that the group without the disease (controls) was exposed (b/d)
70
Formula for Odds ratio
OR= ad/ bc
71
When is Relative risk typically used?
In cohort studies
72
Risk of developing disease in the exposed group divided by risk in the unexposed group divided by risk in the unexposed group
Relative risk
73
Example of Relative risk
If 21% of smokers develop lung cancer vs 1% of nonsmokers, RR= 21/1 = 1
74
Formula for Relative risk
a/(a+b)
RR= -----------
c/(c+d)
75
The proportion of risk reduction attributable to the intervention as compared to a control
Relative risk reduction
76
Formula to determine Relative risk reduction
RRR= 1 - RR
77
Example of Relative risk reduction
If 2% of a patients who receive a flu shot develop flu, while 8% of unvaccinated patients develop the flu, then RR = 2/8 = 0.25, and RRR= 1- RR = 0.75
78
The difference in risk between exposed and unexposed groups, or the proportion of disease of disease ocurrences that are attributable to the exposure
Attributable risk
79
Example of Attributable risk
If risk of lung cancer in smokers is 21% and risk in nonsmokers is 1% then 20% (or .20) of the 21% risk of lung cancer in smokers is attributable to smoking
80
How is Attibutable risk calculated?
a c
AR= ------ - -----------
a+ b c+ d
81
The difference in risk (not the proportion) attributable to the intervention as compared to a control
Absolute risk reduction
82
Example of Absolute risk reduction
If 8% of people who receive a placebo vaccine develop flu vs 2% of people who receive a flu vaccine, then ARR= 8%- 2%= 6% = .06
83
Number of patients who need to be treated for 1 patient to benefit
Number needed to treat
84
How is Number needed to treat calculated?
1/ARR
85
Number of patients who need to be exposed to a risk factor for 1 patient to be harmed
Number needed to harm
86
How is Number needed to harm calculated?
1/AR
87
Characteristics of Precision
The consistency and reproducibility of a test (reliability)
| The abscence of random variation in a test
88
What reduces precision in a test?
Random error
89
What is the effect Increased precision?
Decreases standard deviation
90
Characteristics of Accuracy
The trueness of test measurements (validaty)
| The absence of systematic error or bias in a test
91
What reduces accuracy in a test?
Systematic error
92
Bias nad study errors
Recruiting participants
Perfoming study
Interpreting results
93
What is including in Recruiting participants?
Selection bias
94
Nonrandom assignment to parcipate in a study group
Selection bias
95
What is the most common selection vias?
A sampling bias
96
Examples of selection bias
Berkson bias
Loss of follow up
Healthy worker and volunteer biases
97
Selection bias type that study looking only at inmpatients
Berkson bias
98
Selection bias type Studying a disease with early mortality
Loss of follow up
99
Selection bias type that study populations healthier than the general population
Healthy worker and volunteer biases
100
How is Selection bias reduced?
Randomization
| Ensure the choice of the right comparision/reference group
101
Perfoming study types
Recall bias
Measurement bias
Procedure bias
Observer expectancy bias
102
Definition of Recall bias
Awareness of disorder alters recall by subjects
103
In which studies is common Recall bias?
Retrospective studies
104
Which perfoming study has patients with disease recall exposure after learning of similar cases?
Recal bias
105
Strategy to reduce Recall bias
Decrease time from exposure to follow up
106
Definition of Measurement bias
Information is gathered in a way that distorts it
107
Example of Measurement bias
Hawthourne effect- groups who know they're beingstudied behave differently than they would otherwise
108
Strategy to reduce Measurment bias
Use a placebo control groups with blinding to reduce influence of participants and researchers on experimetal procedures and interpretation of outcomes
109
Definition of Procedure bias
Subjects in different groups are not treated the same
110
Patients in treatment group spend more time in highly specialized hospital units... it is an example or this bias and study error
Procedure bias
111
Definition of Observer expectancy bias
Researcher's belief in the efficacy of a treatment changes the outcome of that treatment (aka Pygmalion effect; self fulfilling prophecy)
112
If observer expects treatment group to show signs of recovery, then he is more likely to document positive outcomes, which type of Perfoming study is?
Observer expectacy bias
113
Types of Interpreting results
Confunding bias
| Lead bias
114
Definition of Confunding bias
When a factor is related to both the exposure and outcome, but not on the casual way → factor distorts of confuses effect of exposure on outcome
115
Example of Confunding bias
Pulmonary disease is more common in coal workers than the general population; however people who work in coal mines also smoke more frequently than general population
116
Strategy to reduce Confunding bias
```
Multiple/repeated studies
Crossover studies (subjects act as their own controls)
Matching (patients with similar charateristics in both treatment and control groups)
```
117
Definition of Lead time bias
Early detectionis confused with increased survival; seen with improved screening techniques
118
Example of Lead time bias
Early detection makes it seem as though survival has increased, but the natural history of the disease has not changed
119
Strategy to reduce Lead time bias
Measure "back-end" survival (adjust survival according to the severity of disease at the time of diagnosis)
120
Statistical distributions
Measures of central tendency
Measures of dispersion
Normal distribution
121
Measures of central tendency
Mean
Median
Mode
122
How is Mean calculated?
Mean= (sum of values)/ (total number of values)
123
What is Median?
Middle value of a list of data sorted from least to greatest
| If there is an even number of values, the median will be the average of the middle two values
124
Most common value
Mode
125
Measures of dispersion
Standard deviation
| Standard error of the mean
126
What is Standard deviation?
How much variability exists from the mean in a set of values
127
What is Standard error of the mean?
An estimation of how much variability exists between the sample mean and the true population mean
128
Characteristics of Normal distribution
Gaussian, also called bell shapped
| Mean= median= mode
129
Nonnormal distributions
Bimodal
Positive skew
Negative skew
130
What does Bimodal distribution suggests?
Two different populations
131
Example of Bimodal distribution
Metabolic polymorphosm such as fast vs low acetylators; suicide rate by age
132
Characteristics of Positive skew distribution
Typically, mean > median > mode
| Asymmetry with longer tail on right
133
Characteristics of Negative skew distribution
Typically, mean
134
Statustical hypotheses
Null (H0)
| Alternative (H1)
135
Hypothesis of no difference
Null hypothesis
136
There is no association between the disease and the risk factor in the population
Null (H0) hypothesis
137
Hypothesis of some difference
Alternative (H1) hypothesis
138
There is some association between the disease and the risk factor in the population
Alternative (H1) hypothesis
139
Outcomes of statistical hypothesis testing
Correct result
| Incorrect result
