Descriptive Statistics

Question 1

Why are statistics important?

Answer 1

• To find the answers to big questions
• Cannot test everyone so a sample is taken and an estimate can be made to say something about the population
• Statistics allow us to make inferences about a phenomenon in the population based on the estimates calculated from a small sample

Question 2

Categorical variable

Answer 2

A category is assigned to each data point
Aka nominal
Eg. Male/Female, smoker/non-smoker, Labour/Lib Dem/Tory

Question 3

Discrete variable

Answer 3

Data points are placed in logical order
Numbers themselves have no meaning
Eg 1st, 2nd 3rd
Aka ordinal

Question 4

Continuous variable

Answer 4

Data points ranked in logical scale
Relative difference between numbers has meaning
Aka scale
Eg. temperature, reaction time, weight

Question 5

What do descriptive statistics do?

Answer 5

Summarise the data

Question 6

What are descriptive statistics?

Answer 6

Measures of central tendency

Measures of dispersion

Question 7

Measures of central tendency

Answer 7

Mean
Median
Mode

Question 8

Measures of dispersion

Answer 8

Variance
Standard deviation
Range

Question 9

Variance

Answer 9

Spread of scores relative to the mean

Squared values

Question 10

Standard deviation

Answer 10

Spread of scores relative to the mean

Normal values

Question 11

Reporting descriptive statistics

Answer 11

‘The average score was calculated (N=…). The mean score was … (SD = …, range = …)’