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Flashcards in Tutorials Deck (18)
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1
Q

What can be estimated from a sample?

A

The true underlying risk in a population can be calculated

2
Q

What is a p value?

A

Probability of obtaining the study result to see whether the null hypothesis is true

3
Q

What does it mean if p<0.05?

A

Null hypothesis is rejected and results are statsistically significant and not due to chance

4
Q

What is the procedure of hypothesis testing?

A
  1. Set up a null hypothesis (e.g. difference in prevalence between the two groups is zero)
  2. Choose an appropriate statistical test
  3. Inspect the results (estimated measure of association – or, in this case, estimated
  4. difference in prevalences – plus its CI and P value) for evidence of real difference: can we reject the null hypothesis?
5
Q

What are ‘odds’?

A

The odds is another way to express probability, e.g. the odds of exposure is the number of people who have been exposed divided by the number of people who have not been exposed.

6
Q

What is the mathematical relationship between odds and probability?

A

Odds= probability/ (1-probability)

7
Q

What is the relative risk?

A

A measure of association between exposure and disease. It is the ratio of the incidence in exposed group/ incidence in non exposed

8
Q

What does a relative risk of 1.0 mean?

A

The incidence of disease in exposed and unexposed are equal

9
Q

What does a relative risk greater than 1.0 mean?

A

Positive association- increased risk among those exposed

10
Q

What does a relative risk less than 1.0 mean?

A

There is a decreased risk among the exposed

11
Q

What is attributable risk?

A

Measure of exposure effect that indicates on an absolute scale how much greater the frequency of disease in the exposed group is than the unexposed, assuming relationship is causal

12
Q

How do you calculate attributable risk?

A

Incidence in exposed - incidence in the unexposed

13
Q

How do you calculate the odds ratio?

A

odds of exposure in cases/ odds of exposure in control

14
Q

What is the odds ratio?

A

In case control studies you can’t calculate the incidence of disease in exposed and non exposed so you calculate the odds of exposure (See notes).

15
Q

What does an odds ratio of 1 indicate?

A

exposure is no more likely in cases than controls

16
Q

What does an odds ratio of more than 1 mean?

A

Exposure is more likely in the case group

17
Q

what does an odds ratio of less than 1 mean?

A

Exposure is less likely in the case group

18
Q

how can you deal with confounding variables?

A

Stratification, standardisation, regression
§ Stratification- a method for controlling the effect of confounding at the analysis stage of a study - risks are calculated separately for each category of confounding variable, e.g. each age group and each sex separately.

§ Standardisation- a method for controlling the effect of confounding at the analysis stage of a study. Used to produce a Standardised Mortality Ratio, a commonly used measure in epidemiology.

§ Regression- a method for controlling the effect of confounding at the analysis stage of a study - statistical modelling is used to control for one or many confounding variables.