Exam 3

Question 1

Probability

Answer 1

Deals with the relative likelihood that a certain event will or will not occur, relative to some other events

Question 2

Probability is a synonym of

Answer 2

proportion

Question 3

Occurrence of an event is just as likely as it is unlikely at probability

Answer 3

0.5

Question 4

Probability values assigned to each experimental outcome must be between

Answer 4

0 and 1

Question 5

The sum of all experimental outcome probabilities must be

Answer 5

1

Question 6

Outcome space/sample space

Answer 6

All possible outcomes.

Mutually exclusive and exhaustive

Question 7

Complement of an event

Answer 7

The complementary event A refers to the event consisting of all sample points that are not in A

Question 8

Probability of intersect (joint)

Answer 8

Probability of both A and B occurring at the same time

Two events A and B that are not mutually exclusive

Question 9

Probability of conjoint (union)

Answer 9

The probability of either A or B occurring

Question 10

Conditional probability

Answer 10

p(A|B)

The probability of an outcome, given that a certain value is already known for a second variable.

Question 11

Non-parametric Chi-square test

Answer 11

Involves discrete variables (categorical data). It does not require assumptions of homogeneity or normality
Nominal (yes/no) data
Evaluating the difference between the frequencies actually observed in the sample

Question 12

Df of chi squared

Answer 12

n-1

(n-1)(r-1) for test of independence

Question 13

Chi squared test, if the calculated value is less than the critical value what happens?

Answer 13

We fail to reject the null hypothesis.

No change

Question 14

Chi square test of independence

Answer 14

To determine if the two discrete variables are independent of each other or if an association exists.
Attempting to find out if one variable predicts another variable.
Data is displayed in a contingency table of rows and columns

Question 15

Chi square, what do we do when the calculated statistic is greater than the critical value?

Answer 15

Reject the null hypothesis

There is a significant difference

Question 16

Assumptions of chi square test of independence

Answer 16

There must be at least one observation in every cell, no empty cells
The expected value for each cell must equal or be larger than 5

Question 17

Yates Chi Square for conservative estimation

Answer 17

Used in certain situations when testing for independence on a contingency table.
Produces a smaller numerator and a more conservative estimate for the chi square statistic; harder to reject null

Question 18

Fishers Exact Test for less data

Answer 18

Used when data for a chi-square test of independence is reduced to 2x2 and the expected values are still too small or have a zero in the cell
Can be non-parametric median test or probability for multiple tests

Question 19

McNemars Test

Answer 19

Will be used to evaluate the relationship or independence of paired discrete variables (like paired T test)

Question 20

When to use OR vs RR?

Answer 20

OR are more commonly reported incase control, cohort studies and clinical trials
OR can be an estimate of RR
If the outcome of interest is rare, OR=RR
Either overestimate (OR>1) or underestimate (OR<1)

Question 21

NNT

Answer 21

The number of patients needed to treat with the specified therapy in order for one patient to benefit.
Inverse of ARR

Question 22

Logistic regression

Answer 22

An extension of multiple regression methods for use where the dependent variable is dichotomous (dead/alive)
Determines the predicted probability of the outcome based on the combo of predictor values

Question 23

Simple logistic regression

Answer 23

Logistic regression with one independent and one dichotomous dependent variable

Question 24

How do you solve the problem of probabilities not being linear?

Answer 24

Transformation to convert into a linear expression

Question 25

How do you transform a probability into a linear expression?

Answer 25

1. ) Convert probability to odds | 2. ) Make natural log of odds

Question 26

b1 regular regression

Answer 26

For a one-unit change in x we expect an average change in Y of b units, holding all other variables constant

Question 27

b1 logistic regression

Answer 27

For a one unit change in x, we expect on average that the predicted odds will change by a multiplicative factor of e^b1 holding all else constant

Question 28

Cox proportional hazard regression

Answer 28

Accounts for the effects of predictor continuous and discrete variables on the dependent variable, which can include censored time-until-event To compare survival in two or more levels of an independent variable adjusting for multiple covariates

Question 29

What is research?

Answer 29

A systematic approach to find answers to questions

Question 30

Applied vs Basic research

Answer 30

Applied- solving problems | Basic- understanding problems

Question 31

Cross-sectional study

Answer 31

It takes place in a single point in time

Question 32

Longitudinal study

Answer 32

Takes place over time. You have at least 2 or more waves

Question 33

Exploratory Research

Answer 33

Invesitgating or discovering something that is previously unknown Zika, Ebola , swine flu

Question 34

Descriptive Research

Answer 34

A systematic attempt to symbolize the obvious relationships that are found among the natural phenomena under study Association between variables, frequency of occurrence

Question 35

Explanatory research

Answer 35

To explain (show causal relations between variables) and predict relations Discovers the answer to the question Reveals gaps in our understanding

Question 36

Research problem

Answer 36

A question demanding a settlement Expresses a relationship between 2 or more variables, usually in the form of a question, should imply a method of empirical testing

Question 37

Research hypothesis

Answer 37

A conjectural statement, a tentative proposition about the relation between two or more variables. It is a prediction from theory under test

Question 38

Bias of systematic error

Answer 38

Causes some type of constant error in the measurement with a system

Question 39

Bias of random errors

Answer 39

Chance errors | Unpredictable and will vary in sign (+ or -)

Question 40

Selection bias

Answer 40

Certain characteristics make potential observations more or less likely to be included in the study It occurs when confounding factors are unevenly distributed between experimental and control groups. Also called cherry picking

Question 41

Funding bias

Answer 41

It is possible that there is a different quality of research between industry funding and trials without external funding. Financial interest may bias interpretation

Question 42

Publication bias

Answer 42

A selective publication of trials with certain results may lead to an exaggeration of effects

Question 43

Reliability

Answer 43

A collection of factors and judgments that, when taken together, are a measure of reproducibility. The consistency of measures

Question 44

Validity

Answer 44

Refers to the fact that the data represents a true measurement A valid piece of data describes or measures what it is suppose to represent

Question 45

Conclusion validity

Answer 45

Is there a relationship between the cause and effect? | Means conclusion we reach about our relationship is reasonable.

Question 46

Internal validity

Answer 46

Is the relationship causal? | Example- whether the program causes the outcome

Question 47

Construct validity

Answer 47

Can we generalize to constructs? If there is a causal relationship in a study, did you measure the outcomes you wanted to measure? Can you claim that the research program reflected your intended construct of the program?

Question 48

External validity

Answer 48

Can we generalize to other persons, places, times?

Question 49

Descriptive data analysis

Answer 49

Range, mean, SD, percentage, CI

Question 50

Inferential statistics

Answer 50

Parametric- tTest, ANOVA | Non-parametric- chi square, logistic regression