semester 2 session 2 measurements

Question 1

properties of a sample

Answer 1

1. representitive
2. unbiased
3. precise

Question 2

types of error

Answer 2

• chance
• bias

Question 3

chance error (random error)

Answer 3

• due to people selected - sampling variation
• doesnt reduce as more people are chosen

Question 4

bias (systematic error)

Answer 4

• difference between the true and expected value
• doesnt reduce by changing the sample size

Question 5

selection bias

Answer 5

1. external valitidy -study sample isnt representitive of the whole population
2. internal validity - groups within the stidy may not be comparable
3. healthy worker effect - workers exhibit lower mortality rate

Question 6

information bias

Answer 6

1) recall error - different recollection of data
2) interviewer error - interviewer has pre concieved expectations that influences result
3) measurement error - with scales
4) misclassification - participants have been put in the wrong group

Question 7

does bias decrease as you increase study

Answer 7

no

bias stays the same

Question 8

prevalence

Answer 8

• proportion who have the disease at any given point in time

number of people with disease / population

Question 9

incidence

Answer 9

• number of new cases in a given time

number of new patients / patient time at risk

Question 10

what factors effect prevelence

Answer 10

• number of new cases coming in
• how many people dont have it due to cure or death

Question 11

incidence rate ratio

Answer 11

compatres incidence rates between different groups of people

incidence rate in group A / B

Question 12

odds calculation

Answer 12

if the probability of a certain event is p the the odds of the event is

p

1-p

Question 13

odds ratio

Answer 13

relative comparison:

odds of group A (diseased/ not diseased)

odds of B (diseased / not diseased)

if answer is > 1 then there is a greater risk of the event

if answer is < 1 then there is a lower risk of the event k