Session 2

Question 1

What is a sample average?

Answer 1

Same as the mean of a sample

Question 2

How do sample means usually look?

Answer 2

All look similar regardless of population

Question 3

What is the average of the means of the sample?

Answer 3

Mean of the population values

Question 4

What is the distribution of the means of samples?

Answer 4

Normal Gaussian distribution

Question 5

What is a confidence interval?

Answer 5

95% confidence interval contains the mean of the population values 95% of the time

Question 6

What is the purpose of statistics?

Answer 6

To generalise and infer about a population

Question 7

What is a sample

Answer 7

As a representative as possible of the population

Question 8

What happens if there is a wider 95% confidence interval?

Answer 8

Greater variation in population values

Smaller the size of the sample used to calculate

Question 9

What is precision?

Answer 9

Exact and accurate

Question 10

What is bias?

Answer 10

Of or on a target

Something has no bias- on a target

Question 11

What is selection bias?

Answer 11

Errors due to systematic differences in the ways in which the two groups were collected

Question 12

What is information bias?

Answer 12

Errors due to systematic misclassification of subjects in the group
Differential recall errors especially in case control studies
Differential observer or interviewer errors
Differential measurement error
Differential mis-classification

Question 13

Give a confounding factor example

Answer 13

Distort results and give misleading results
E.g. People in Bournemouth have higher levels of cancer but age is a confounding factors as older people are more likely to have cancer but also more likely to live in Bournemouth

Question 14

What is prevalence?

Answer 14

Incidence x duration of disease

The amount of people who currently have the disease

Question 15

What is Incidence?

Answer 15

Number of new cases of the disease per 1000 people per year

Question 16

What is a cohort study?

Answer 16

Recruiting disease free individuals and classifying them according to their exposure status, they are then followed up for extending periods and disease progress and Incidence rate is calculated

Question 17

What is a case-control study?

Answer 17

Recruiting disease free individuals and diseased individuals and then there exposure status is then determined

Question 18

What is a confounding factor?

Answer 18

Something that is associated with both the outcome and the exposure of interest but is not on the casual pathway between exposure and outcome

Question 19

Why are Case control studies heavily bias?

Answer 19

Selection bias- not representing the general population

Recall bias- exposure status incorrectly determined as looking back at history

Question 20

What is risk ratio?

Answer 20

Ratio of prevalence portions of outcome in groups defined by levels of exposure at a particular time

Question 21

What is rate ratio?

Answer 21

Ratio of incidence rates of outcome in groups defined by levels of exposure after a particular time period

Question 22

What is odds ratio?

Answer 22

Ratio of odds of outcome in groups defined by levels of exposure at a particular time

Question 23

What is a cross section survey used for?

Answer 23

Analysed to give prevalence

Question 24

What can be calculated from a cohort study?

Answer 24

Risk ratio
Incidence rate ratio
Odds ratio

Question 25

What can be calculated from a control study?

Answer 25

Odds ratio