Critical numbers

Question 1

What is prevalence probability?

Answer 1

Probability of having a disease at a given point in time

Question 2

Incidence probability

Answer 2

Probability of getting a disease during a specified point in time

Question 3

Incidence rate

Answer 3

average rate of change over time

Question 4

Hazard rate

Answer 4

Instantaneous rate of change

Question 5

Incidence

Answer 5

Number of people newly diagnosed

Question 6

Prevalence

Answer 6

new and pre-existing cases

Question 7

Probability equation

Answer 7

P = no. of case/ total population

Question 8

Odds equation

Answer 8

odds = cases/non-cases

Question 9

Absolute risk definition

Answer 9

Difference between 2 risks

e.g. 4 in 100 risk of non-smokers developing a disease

Question 10

Relative risk definition

Answer 10

Ratio between 2 risk

e.g. risk of getting a disease is increased for smokers

Question 11

What are the 4 different observational studies?

Answer 11

1) Cross-sectional
2) Case-control
3) Cohort
4) Ecological

Question 12

What is a cross-sectional study?

Answer 12

Observations made at a specific point in time (now)

Question 13

Strengths and weaknesses of a cross sectional study?

Answer 13

Strengths

• Fast, inexpensive
• who currently has exposure and outcome
• no follow up

Weaknesses

• not suitable for rare diseases
• difficult to establish order of events
• Can’t find causes

Question 14

What is a case control study?

Answer 14

(Past) select participants with and without outcome and look back to see who had exposure

Question 15

Strengths and weaknesses of case control study?

Answer 15

Strengths

• suitable for rare diseases
• multiple exposures can be studied
• quick

Weaknesses

• only a single disease can be studied
• difficult to establish order of events
• affected by selection bias & confounding factors

Question 16

What is a cohort study?

Answer 16

(future)
collect participants info on a sample (some have exposure, others don’t)
Follow up over time, see who gets outcome

Question 17

Strengths and weaknesses of cohort study?

Answer 17

Strengths

• useful for demonstrating causal effect
• multiple diseases & exposure can be studied
• less chance of bias

weaknesses

• time consuming and expensive
• not suitable for rare diseases
• people drop out

Question 18

What are the 2 experimental studies?

Answer 18

Randomised control trial and crossover

Question 19

What is an RCT? Pros and cons?

Answer 19

Participants randomised to groups and followed up to compare outcomes
Strengths
- 'gold standard'
- prevents bias - can be double blinded
- shows cause and effect
Weaknesses
- expensive
- not suitable for long term effects
- not always ethical 
can be effected by non-compliance

Question 20

What is a crossover trial? pros and cons?

Answer 20

Everyone in the study has all arms of the trial at some point

• order of each arm randomised
• everyone is their own comparison

Cons

• more technical analysis
• not always suitable (if drug/ surgery has carry over effects)

Question 21

Association vs causation

Answer 21

Association = a statistical link between exposure and disease

Causation = a statistical link where a disease is directly caused by the exposure

Question 22

What is simple random sampling?

Answer 22

Each member of the population has an equal probability of being selected

• computer generated
• not always good representation
• not precise

Question 23

What is systematic random sampling?

Answer 23

Members of the population are selected at equal intervals

cons

• need complete list of population
• large standard error
• periodicity patterns>characteristics that occur at intervals

Question 24

What is stratified random sampling?

Answer 24

population is split into groups and samples are taken from each group 
Pros
- increases representation
- smaller standard error
cons
- requires prior info about population
- expensive

Question 25

What is cluster sampling?

Answer 25

Population is partitioned into clusters and a sample of clusters is selected (clusters similar) - complete list of population not needed - cheaper cons - clustering decreases statistical precision (higher standard error)

Question 26

Standard deviation vs standard error

Answer 26

``` SD = within a sample SE = between samples ```

Question 27

P -value

Answer 27

p < 0.05 indicates statistical significance

Question 28

Crude vs adjusted effects

Answer 28

Crude = does not take into account confounding variables Adjusted = accounts for confounding factors

Question 29

Biochemical, chemical or hormonal stress?

Answer 29

Metabolic changes due to stress | - endorphin levels altered

Question 30

Signs of physiological stress?

Answer 30

Physiological signs of stress - shallow breathing - raised blood pressure - increase in acid production in the stomach

Question 31

Signs of emotional stress?

Answer 31

Emotional signs of stress: - mood swings - tearful - irritable - aggressive - apathetic

Question 32

Cognitive stress signs?

Answer 32

- Negative thoughts | - loss of concentration

Question 33

Behavioural signs of stress?

Answer 33

- Increases absenteeism - smoking - alcohol consumption - change in food consumption - sleep disturbances

Question 34

What are the two types of emotional responses to stress?

Answer 34

Positive affect | Negative affect

Question 35

Social signs of stress?

Answer 35

Similar to behavioural - social relationships - participation in activites/work

Question 36

What is primary prevention?

Answer 36

prevention of disease in people who have not been diagnosed as having the disease, includes health promotion

Question 37

What is secondary prevention?

Answer 37

Early detection of disease | - followed by appropriate intervention

Question 38

What is the high risk approach to prevention?

Answer 38

targeting of health promotion and disease prevention at groups based on info from epidemiological studies

Question 39

What is the population approach to prevention?

Answer 39

Aims to lower the level of risk in the population, includes health promotion

Question 40

What is tertiary prevention?

Answer 40

Aims to reduce the impact of the disease and promotes quality of life through active rehabilitation

Question 41

What is the preventing paradox?

Answer 41

A preventive measure which brings much benefit to the population, may offer little to each participating individual

Question 42

What aspect of the relationship between occupation and asthma could only be examined through prospective studies? a. Association b. causation c. analytical d. descriptive e. Qualitative

Answer 42

B Causation: the existence of a causal relationship between variables; the cause must precede the effect

Question 43

What is an ecological study?

Answer 43

Uses routine date from populations | - looks at prevalence, trends and correlations

Question 44

What is a longitudinal study?

Answer 44

Observational study of persons over a period of time taking measurements at more than one time point

Question 45

What does it mean if there is a big difference between mean and median?

Answer 45

It is not normally distributed

Question 46

If a study is not normally distributed which data should you use? (e.g. mean, median, SD, SE, IQR)

Answer 46

Median

Question 47

What analytical value do you pair with median?

Answer 47

IQR | mean and SD

Question 48

Which of the following is incorrect? The standard error of the mean of a sample:   a. Can be calculated using the standard deviation and the size of the sample b. Measures how far the sample mean is likely to be from the population mean c. Is used in the calculation of a confidence interval d. Is greater than the standard deviation of the observations e. Should only be calculated when the sample is normally distributed

Answer 48

D. The SE will be smaller than the SD

Question 49

What is linear regression?

Answer 49

Models the dependency of Y with a change in X - can have positive, negative or no correlation - can remove background association to reveal a clearer picture of the relationship between the main exposure of interest and outcome

Question 50

What is multi-variable regression?

Answer 50

Adjust for all the variables in the model

Question 51

What is opportunity cost?

Answer 51

To spend resources on one activity means a sacrifice in terms of a lost opportunity cost elsewhere

Question 52

What is economic efficiency?

Answer 52

It is achieved when resources are allocated between activities in such a way as to maximise benefit.

Question 53

What is QALYs?

Answer 53

Quality Adjusted Life Year | - combines length of life with quality of life

Question 54

What are the 4 types of economic evaluation?

Answer 54

``` 1) Cost effectiveness analysis (measure in natural units e.g. change in BP) 2) Cost-utility analysis (measured in QALYs) 3) Cost-benefit analysis (measure in monetary units) 4) Cost-minimisation analysis ```

Question 55

Cost effectiveness ratio?

Answer 55

Difference in costs/difference in benefits

Question 56

What is observer bias?

Answer 56

When variables are reported differently between assessors

Question 57

What is selection bias?

Answer 57

error in the process of selecting participants for the study and assigning them to particular arms of the study

Question 58

What is measurement bias?

Answer 58

When information is recorded in a distorted manner (inaccurate tool)

Question 59

What is procedure bias?

Answer 59

Subjects in different arms of the study are treated differently

Question 60

What is Misclassification bias?

Answer 60

Occurs when a variable is classified incorrectly