Lecture 3 - Measurements

Question 1

What is Descriptive epidemiology?

Answer 1

When the burden of a disease is measured

How frequently does it occur?
How quickly does it occur?

Question 2

What is analytical epidemiology?

Answer 2

Measures the causes and effects

How and why does it occur

Question 3

What is incidence?

Answer 3

The number of new cases within a given period of time

Question 4

What is prevalence?

Answer 4

The number of existing cases within a given period of time

Question 5

What is the equation for incidence risk?

Answer 5

Num of new cases in a certain time / size of case freee population at start of period

Question 6

What is the incidence rate equation?

Answer 6

Num of new cases during a certain time / the time each person was observed totalled for all people

Question 7

What is the prevalence rate equation?

Answer 7

All new and pre-existing cases durin a given time period / population during same time period

Question 8

What actually is incidence rate?

Answer 8

How quickly a disease occurs in a population not a proportion

Question 9

What is the difference between incidence and prevalence?

Answer 9

Incidence only involves NEW cases
Prevalence involves BOTH pre existing and NEW cases

Question 10

What should the Incidence risk and prevalence rate be like for Short lived diseases?

Answer 10

Incidence risk and prevalence rate should be SIMILAR

Question 11

What is Case-fatality rate?

Answer 11

The incidence risk of a specific cause

E.g num of patients died of influenza

Question 12

What is mortality rate?

Answer 12

Incidence rate all or specific. Cause

E.g number of people who die in a year per 100,000 of population

Question 13

How is incidence risk clinically relevant?

Answer 13

If u think a patient may have 1 of 2 diseases you’d order the test with the higher incidence risk

Question 14

How can incidence risk be used to see if theres a relationship between smoking and lung cancer?

Answer 14

Have 2 groups of people :
Smokers + Non smokers

Will find that the incidence risk of lung cancer in smokers is higher than in the non smokers

Question 15

When a study is done on 2 groups of people where 1 group given antivirals and the others no antivirals to see if an antiviral is effective in reducing mortality.
What is the cause and what is the effect?

Answer 15

Cause = antiviral
Effect == death due to viral infection

Question 16

What is Risk ration and odds ratio use to measure?

Answer 16

QUaitfy the strength of association between the exposure and event

Question 17

What are 3 potential cause and effect isssues that can falsify the finding?

Answer 17

Confounding
Chance
Bias

Question 18

What is a confounder?

Answer 18

Other factors which are associated witht the exposure and outcome which aren’t considered which may falsify findings

Question 19

How can chance falsify a finding?

Answer 19

The observed association may happen by chance (random error)

Question 20

How can bias affect/falsify findings?

Answer 20

There may be errors in the data collection, analysis and interpretation that lead to results that are systematically different from the truth

Question 21

How does increasing the sample size help decrease chance falsifying findings?

Answer 21

The larger the sample the more closely the sample reflects the whole population so any odds ratios calculated are more likely to match the population

Question 22

What is selection bias?

Answer 22

When the sample is not representative of the population

Question 23

When many individuals have been sampled in a study and they have the lung cancer gene, what type of bias is this?

Answer 23

Selection bias

Question 24

What is confounding bias?

Answer 24

The effect of exposure on outcome is mixed with another factor

Question 25

What type of bias is this?

Age of individuals are not taken into account when calculation odds ratio?

Answer 25

Confounding bias

Question 26

What is recall bias?

Answer 26

Incomplete/inaccurate recollection of info by participants

(Can’t remember if they smoked or said the wrong answer)

Question 27

What type of error does bias cause?

Answer 27

Systematic error

Question 28

What type of error does bias cause?

Answer 28

Systematic error

Question 29

What type of association is indicated by an odds ratio or Risk ratio being equal to 1?

Answer 29

When OR or RR = 1
NO ASSOCIATION BETWEEN EFFECT AND OUTCOME

Question 30

What type of association is indicated by an odds ratio or Risk ratio being less than 1?

Answer 30

OR or RR less than 1 = NEGATIVE ASSOCIATION BETWEEN EFFECT AND OUTCOME

Question 31

What type of association is indicated by an odds ratio or Risk ratio being more than 1?

Answer 31

OR or RR more than 1 = POSITIVE ASSOCIATION BETWEEN EFFECT AND OUTCOME

Question 32

How would you work out the Risk Ratio (RR) for people who are smokers getting lung cancer to non smokers getting cancer?

Answer 32

Do num smokers with lung cancer DIVIDED by TOTAL num of smokers (say value obtained is x)

Do num of Non smokers with lung cancer DIVIDED by TOTAL num of non smokers (say value obtained is y)

Then do x DIVIDED by y to get the RR

Question 33

How would you work out the Odds Ratio (RR) for people who are smokers getting lung cancer to non smokers getting cancer?

Answer 33

Do num of smokers with lung cancer DIVIDED by num of smokers WITHOUT lung cancer (say this value is x)

Do num of non smokers with lung cancer DIVIDED by num of non smokers WITHOUT lung cancer (say this value is y)

Then do x / y to find odds of having lung cancer compared to non smokers

Question 34

What value is not used to calculate odds ratio?

Answer 34

TOTALS ARE NOT USED