Biostats

Question 1

Relative risk equation?

Answer 1

RR = risk of an outcome in an exposed group/ risk of the same outcome in an non exposed group

Question 2

What is a cross sectional analysis and what is it used for?

Answer 2

Data gathers at one point in time
Can determine prevalence of an outcome in a population
Identify specific risk factors and help generate hypothesis for further research

Question 3

False negative equation?

Answer 3

FN = 1- sensitivity x number of pts who truly have the disease

Question 4

True positive equation?

Answer 4

TP= Sensitivity x number of patients who truly have the disease

Question 5

Meta analysis

Answer 5

Groups results of several trials to increase statistical power and provide overall pooled effect estimates

Question 6

How to determine if CI is statistically significant

Answer 6

For odds ratio and relative risk the null value is 1 ( as long as CIS do not cross the null value it is statistically significant)

For difference the null value is 0

Question 7

Two sample test

Answer 7

Statistical method to compare the means of 2 groups of subjects

Question 8

P value in a study with a large number of pts

Answer 8

A smaller p value is used to decrease the risk of of false positive results

Question 9

Precision of test

Answer 9

Precision ( reliability) is the ability of the test to reproduce identical results with repeated measurements

Question 10

Health promotion

Answer 10

Is an e.g of 1o prevention
Enabling people to control their health and determinants

Question 11

Observer bias

Answer 11

Occurs with the investigator’s evaluation is affected by preconceived expectations or prior knowledge leading to overestimation

Question 12

Independent event probability

Answer 12

If you have multiple independent events you multiply the probability

Question 13

Prospective cohort study

Answer 13

Patients are selected on their exposure status and followed up over time for development of disease

Question 14

Risk equation

Answer 14

Risk of developing the disease with exposure/ all subjects who were exposed

Question 15

Main purpose of blinding in a study is to prevent

Answer 15

Observer bias by either pt or researcher

Question 16

Area under the curve

Answer 16

The more accurate a test is ( high sensitivity and specificity) the closer AUC value is to 1

Question 17

The average of a dataset of values

Answer 17

Equivalent to mean
Total number of episodes/total number of pts

Question 18

Allergic contact dermatitis features

Answer 18

Type IV hypersensitivity reaction
Intercellular epidermal oedema, with infiltration of lymphocytes and eosinophils

Question 19

Reducing significance set alpha in a study will lead to

Answer 19

Any significant findings will be reported with greater confidence

Decreased significance level = increased confidence level

Question 20

Cross sectional study

Answer 20

Exposure and outcome measured simultaneously at a particular point in time
Prevalence study

Question 21

Positively skewed curve relationship between mean, median and mode

Answer 21

Mode is closer to the middle and mean closer to tail ( RT tail)
Median in the middle
Mode <median < mean

Question 22

Attack rate equation

Answer 22

Number of people who contact an illness/ number of people who are at risk of contracting that illness

Question 23

Prevalence can be increased by

Answer 23

Incidence or prolonged disease duration

Prevalence = incidence x disease duration

Question 24

Normal distribution mean and median

Answer 24

In a normal distribution curve mean and median are equal therefore 50% of observations will lie below the mean and 50% above

Question 25

Lead time bias

Answer 25

When a test diagnoses a condition earlier than conventional causing an apparent increase in survival time but no improvement on actual time to mortality

Question 26

Negative predictive value

Answer 26

Probability that an individual doesn’t have the disease given a negative result

NPV= TN/ TN+FN

Question 27

Misclassification bias

Answer 27

Incorrect categorization of subject re: their outcome status or both

Question 28

Hawthorne effect

Answer 28

Tendency of the study subjects to change their behaviour as a result of awareness that they are being studied

Question 29

Greatest preventive intervention in almost all patients

Answer 29

Smoking cessation

Question 30

T test ( paired t test )

Answer 30

Compares the mean of 2 groups
Quantitative test

Question 31

Precision and accuracy

Answer 31

High precision it consistently provides same or similar value
High accuracy test provides measurements see or similar to actual value

Question 32

Absolute risk reduction

Answer 32

Event rate in control group - event rate in the treatment group

Event rate in treatment= # of event in treatment arm / # of subjects

Question 33

Absolute risk increase

Answer 33

Difference in the rate (risk ) of the adverse event between treatment and control group

ARI= Rate AE treatment - Rate AE control

Question 34

Number needed to harm

Answer 34

NNH= 1/ ARI