Measuring Disease In Populations

Question 1

Prevalence of a disease

P ~ (I x L)

Answer 1

The number of people affected by the disease.

Increases if incidence increases and if sufferers are kept alive for longer

Question 2

Incidence of a disease

Answer 2

Measures the number of new cases of disease

Decreases if more sufferers are cured or if more sufferers die

Question 3

Tendency and Observation

Answer 3

The ‘observed’ value is the best estimate we have of the ‘true’ or ‘underlying’ tendency.
Allows us to test hypotheses about the ‘true’ value.

Question 4

Ho - the null hypothesis.

The hypothesis that there is no difference between the two populations.

Answer 4

The value of 1 is within/out of the 95% CI.
The p value is greater/less than 0.05.
There is insufficient/sufficient evidence to regret Ho at the 95% level.
There strong evidence for/against the hypothesis that the _____.

Question 5

Confidence Interval

gets smaller with more data - the results are less effected by chance.

Answer 5

Lower 95% CI = observed value / e.f.

Upper 95% CI = observed value x e.f.

Question 6

Incidence Rate Ratio
(IRR)
Relative Risk

Answer 6

observed / (population x years)
compare to 1 or 100
always say e.g. 1.9 times AS likely to develop ____ in population A compared to population B.
use IRR to x or / by e.f. to work out CI.

Question 7

Standard Mortality Rate
(SMR)
Absolute Risk

Answer 7

observed / expected x 100

use SMR value x or / by e.f. to work out CI.