Summary statistics I

Question 1

What is a variable?

Answer 1

denoted anything that varies within a dataset, categorical or numeric

Question 2

Difference between categorical and numeric values?

Answer 2

Categorical: binary/ ordinal/ nominal

Numerical: discrete/ continuous

Question 3

What is binary data?

Answer 3

Type of categorical data
Data that only has two categories
e.g. positive/negative

Question 4

What is ordinal data?

Answer 4

Type of categorical data
Categories with natural order
e.g. stages of cancer/ levels of pain

Question 5

What is nominal data?

Answer 5

Type of categorical data
Categories with no natural or universally agreed order
e.g. blood group

Question 6

What is discrete data?

Answer 6

Type of numeric data
Observations that can only take certain numerical values
e.g. number of children

Question 7

What is continuous data?

Answer 7

Type of numeric data
Observations can take any value within a range
e.g. height/ temperature

Question 8

Why is categorisation of continuous variables sometimes frowned upon? e.g. age in yrs into age categories

Answer 8

May lead to loss of information
Especially if using arbitrary thresholds

Question 9

What is prevalence? (context categorical data)

Answer 9

Number of existing cases in a population at a defined timepoint

Question 10

What is incidence? (context categorical data)

Answer 10

Number of new cases in a population over a defined period

Question 11

What is used to describe the prevalence of a condition or the probability of an event?

Answer 11

Proportion
Number experiencing the event divided by the total, often reported as a percentage or given per quantity of people e.g. per 1000

Question 11

Difference between prevalence and incidence?

Answer 11

prevalence: existing cases, defined time point
incidence: new cases, defined period of time

Prevalence includes all cases but incidence only includes new cases
Prevalence is dependent on both incidence and duration of the event