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Flashcards in BIO stats Deck (58):
1

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

Interval and Ratio 

Ratio has a meaningful zero age, ht, wt

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

2

Discrete data is also referred to as? 

What are the different types and examples of them?

Nominal: Order is arbitrary  (gender, ethnicity)

Ordinal ranked in logical order pain scale 0,10 

3

The mean is preferred for what type of data?

continuos and normally distributed data

4

What is the mean preferred for? 

preferred for ordinal or continuous data that is skewed 

5

The mode is preferred for what data?

nominal 

6

Continuous data tends to follow what?

A normal distribution 

7

68% fall within how many?

95%?

within 1 SD
within 2 SDs 

8

When is skewed data likely to occur? 

If sample size is small and or there are outliers 

9

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

How can the distortion of outliers be reduced?

Median is the best judge

Distortion can be reduced with increased sample size 

10

Right and left skew?

low values to the right positive right skew

left, negative left skew 

11

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

12

Confidence interval =?

CI=1- alpha 

13

When are the results statistically significant?

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

If the confidence interval doesnt include zero 

 

Statistically significant if values CI does not contain 1 

14

What is a type 1 error?

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 

15

Type 2? 

Accepting the null when the null is false (b)

16

What is power? 

the probability that the test will reject the null hypothesis correctly 

17

How is power calculated?

1-B

18

why is absolute risk reduction more useful?

because it includes the reduction in risk and the incidence rate

19

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

means 12% out of every 100 pts benefited from tx

20

How do you round NNT?

NNH?

When do you use absolute value?

52.1 round to 53 

NNH: 41.9 round down to 41 

When calculating NNH use ARR absolute vlue 

21

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

How do you calculate OR?

Case-controlled studies 

OR= AD/BC

22

When are hazard ratios used?

survival analysis (analysis of death or disease progression) 

23

HR and OR interpretation?

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 

24

Notes on composite endpoints

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