# Multivariate Statistical Analysis and Modeling Flashcards

1
Q

what are statistics used for?

A

to discern justifiable differences in quantitative patterns

2
Q

give 3 classic statistical tests and why they are not practical for epidemiology

A
1. basic t tests
2. ANOVA
3. Chi squared
too burdensome to apply to situations where multiple variables and their interactions are in question
3
Q

describe the T test and give an example of how it could be used

A

tests whether significant differences, not attributable to random chance, are present in continuous data; could use for averaging hemoglobin levels in two different groups of people

4
Q

what does the chi squared test do? give an example

A

tests significance between groups of non-continuous data
examples are infected versus not infected, vaccinated or not vaccinated

5
Q

what are chi squared tests useful for?

A

2x2 contigency tables

6
Q

what is Fisher’s exact test?

A

tests for significance in much the same way as the chi squared test does, but works with ANY SIZE DATA SET!!

7
Q

what does the Fisher’s exact test give?

A

gives an exact P value rather than an approximation like other tests do

8
Q

what can Fisher’s exact test also be applied to?

A

2x contigency tables

9
Q

what is mutlivariable regression? (2)

A
1. multiple independent variables are regressed on a single dependent variable
2. all variables are considered together to discern correlations either individually or in combinations
10
Q

what does multivariate analysis allow for?

A

allows more than two variables to be analyzed at once

11
Q

is multivariable regression a type of multivariable analysis?

A

not usually considered under the heading, but is technically multivariate analysis

12
Q

what are the 2 general types of multivariate analysis technique?

A
1. asnalysis of dependence
2. analysis of independence
13
Q

describe the analysis of dependence multivariate analysis technique

A

where one or more variables are dependent variables, to be explained to predicted by others

14
Q

give 3 analysis of dependence multivariate analysis tests

A
1. multivariable regression
2. PLS (partial least squares)
3. MDA (multiple discriminant analysis)
15
Q

where is multivariable regression analysis often seen?

A

in cohort studies

16
Q

describe the analysis of independence multivariate analysis method

A

no variables are thought of as dependent, just look at the relationship among variables, objects, or causes

17
Q

give 2 analysis of independence multivariate analysis tests

A
1. cluster analysis
2. factor analysis
18
Q

in most cases, why is data anlaysis done?

A

to test the association between two or more variables (bivariate)

19
Q

what is often the aim of analysis in health research?

A
1. to establish the association between risk factor and disease
2. to establish the association between therapy and outcome (patient oriented research)
20
Q

what are the 2 types of regression models?

A
1. simple linear (y = mx+b)
2. multiple linear regression (y = b + m1x1 + m2x2…)
21
Q

what is a model?

A

a set of theoretically and/or evidence based associations between variables

22
Q

what does data analysis test?

A

data analysis tests the extent to which the proposed theoretical associations are observed in the data

23
Q

what is model development based on?

A

model development is based on previous knowledge (previous research evidence about associations)

24
Q

what is model development mostly about?

A

model development is mostly about deciding which independent variables (risk factors) should be in the multivariate analysis

25
Q

what do SIR models mean/stand for?

A

S: susceptible, S(t): the disease-susceptible people in a population
I: infectious, I(t): those capable of transmitting an infection to others
R: recovered R(t): those that have been infected and recovered

26
Q

what do vaccines do in terms of the SIR model?

A

try to move people from susceptible to recovered (since vaccine is like a mini infection)

27
Q

what are the 3 assumptions of the Kernack-McKendrick model?

A
1. assumes a well-defined, closed, and fixed population
2. assumes an infected person is instantaneously infective and infectivity lasts duration of disease state
3. assumes a homogenous population with no genetic variation or demographic differences