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BIO stats Flashcards

1
Q

Continuos data what are the types and the differences of each and examples/

A

Interval and Ratio

Ratio has a meaningful zero age, ht, wt

Interval no meaningful zero, celsius (equal distance between values)

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2
Q

Discrete data is also referred to as?

What are the different types and examples of them?

A

Nominal: Order is arbitrary (gender, ethnicity)

Ordinal ranked in logical order pain scale 0,10

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3
Q

The mean is preferred for what type of data?

A

continuos and normally distributed data

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4
Q

What is the mean preferred for?

A

preferred for ordinal or continuous data that is skewed

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5
Q

The mode is preferred for what data?

A

nominal

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6
Q

Continuous data tends to follow what?

A

A normal distribution

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7
Q

68% fall within how many?

95%?

A

within 1 SD
within 2 SDs

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8
Q

When is skewed data likely to occur?

A

If sample size is small and or there are outliers

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9
Q

What is the best measure of central tendency when you have outliers?

How can the distortion of outliers be reduced?

A

Median is the best judge

Distortion can be reduced with increased sample size

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10
Q

Right and left skew?

A

low values to the right positive right skew

left, negative left skew

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11
Q

If the alpha is 5% what does the p-value need to be to reject the null hypothesis?

A
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12
Q

Confidence interval =?

A

CI=1- alpha

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13
Q

When are the results statistically significant?

Is there a difference with ratio data? (RR, OR, HR)

A

If the confidence interval doesnt include zero

Statistically significant if values CI does not contain 1

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14
Q

What is a type 1 error?

A

Rejecting the null when the null is true

saying there is a difference when there is none

p value correlated to probability of type 1

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15
Q

Type 2?

A

Accepting the null when the null is false (b)

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16
Q

What is power?

A

the probability that the test will reject the null hypothesis correctly

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17
Q

How is power calculated?

A

1-B

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18
Q

why is absolute risk reduction more useful?

A

because it includes the reduction in risk and the incidence rate

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19
Q

ARR of 12% in metoprolol vs placebo trial what does it mean?

A

means 12% out of every 100 pts benefited from tx

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20
Q

How do you round NNT?

NNH?

When do you use absolute value?

A

52.1 round to 53

NNH: 41.9 round down to 41

When calculating NNH use ARR absolute vlue

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21
Q

What kind of studies use odd ratio instead of relative risk?

How do you calculate OR?

A

Case-controlled studies

OR= AD/BC

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22
Q

When are hazard ratios used?

A

survival analysis (analysis of death or disease progression)

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23
Q

HR and OR interpretation?

A

If OR or HR = 1 the event rate is the same

> 1 event rate is higher in treatment group

<1 event rate is lower in tx group

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24
Q

Notes on composite endpoints

A

must be similar in magnitude and have similar meaningful importance to the pt

Use the composite endpoint value instead of adding them all up

25
What test should be used for continuous data?
normal distribution (parametric test) Nonnomral (nonparametric)
26
When is a T-test used? when is a student t-test usd?
with continuous and normally distributed data Student t-test 2 independent variables, medication and placebo
27
When is an analysis of variance used? (ANOVA)
or F-test is used to when continuous data with 3 or more sample groups
28
What test is used when nominal or ordinal data is used?
Chi-squared test
29
What test is used for correlation? What is it used for?
Spearmans ranked order correlation (RHO) ordinal or ranked data
30
What test is used for continuous data correlation?
Pearsons Correlation Coeffieicent r which indicates the strength and direction of correlation (-1 to +1)
31
When are regressions used? What are the 3 types and what are they each used for?
described the relationship between a dependent variable and one or more independent variables commonly used in observational studies Linear: continuous data Logical for categorical Cox regression for categorical in survival analyisis
32
If the test result is positive what is the likelihood of having the disease? If the test is negative what is the likelihood of not having the disease?
33
If a sensitivity is 100% what does that mean?
test will be positive in all patients with the condition
34
100% specificy?
100% of negative patients will not have the disease
35
Specificity is the percentage of?
True negative results
36
Sensitivity and Specificity Formulas
Sensitivity: A/(A+C) x 100 Specificity: D/(B+D) x 100
37
What two ways can data from clinical trials be analyzed?
Intention to treat and per protocol analysis
38
NonInferiority and Equivalence trials
Equivalence new drug is as good as Non-inferiority: new drug is not much worse
39
When are forest plots used?
Composite endpoints in one study or meta-analysis
40
Forest plots
* Boxes show the effect estimate, in meta-analysis the bigger the box the more effect from the study is seen * Diamonds: represent pooled results from multiple studies * Horizonal line is the length of the confidence interval * Vertical line: Line of no effect, left illustrates significant benefit, to the right shows significant harm
41
Case control study
* Pts with disease (cases) to those without (control), * Retrospective * OR,
42
Cohort Study
Compares outcomes of a group of pts exposed and not exposed Groups are followed prospectively
43
Cross-sectional survey
* Estimates the relationship between variables and outcomes (prevalence) at one particular time (cross section) in a defined population
44
Case report and case series
* Describes an adverse reaction or a unique condition that appears in a single pt (case report) or a few pts (series) * No real conclusions can be drawn
45
RCTs
* Compared an experimental tx group to a control (placebo or existing tx) to determine which is better, subjects with the design characteristics (inclusion criteria)
46
Benefits and Limitations of Cross over RCT
* Pts serve as there own control this minimizes effects of confounders * A washout period between tx is needed to minimize influence of the first drug during second tx
47
Factorial design
Randomized to more than the usual to * Evaluates multiple interventions in a single experiment * With every arm added the more subjects you need
48
Meta-Analysis
* Smaller studies can be pool instead of performing a large one * Studies may not be uniform, validity can be compromised if lower quality studies are weighted equally to higher studies
49
Systemic Review article
* Summary of clinical literature that targets something specific * Inexpensive
50
Methods for pharmacoeconomic analysis? 4
* Cost effectiveness analysis * Cost-minimization analysis * cost utility analysis * cost benefit analysis
51
What do pharmacoeconomic studies serve to do
Guide optimal healthcare resource allocation
52
What model is used to evaluate outcomes?
ECHO * Economic * Clinical * Humanistic Outcomes
53
Incremental cost effectiveness ration calculation
C2-C1/ E2-E1
54
When is cost-minimization analysis used?
when two or more interventions have shown equivalence in outcomes and the cost of the interventions are compared
55
Cost Benefit Analysis
comparing benefits and costs of an intervention in terms of monetary units
56
Advantage of Cost Effectiveness Analysis
outcomes are easier to quantify most common analysis Input dollars output clinical (LDL level) Disadvantage: unable to directly compare different types of outcomes (Diabetes program vs. Asthma program: cant do that)
57
What is Cost Utility Analysis?
specialized form of CEA that include a quality of life component using quality adjusted life years (QALY) and disability adjusted life years (DALYs) About quality not quanitity takes into account morbidity and mortality
58

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