STATS1- Preliminaries & descriptive stats

3 types of variables

• categorical

• continuous (numerical)

• discrete (numerical)

what are the measures of central tendency

• mean

• median

• mode

what are the measures of spread

• range

• standard deviation

• variation

what are the steps to calculate sample variance

1. calculate mean

2. calculate how much each score deviates from the mean (±)

3. add deviations & divide by (n-1)

what are the steps to calculate standard deviation

1. calculate mean

2. calculate how much each score deviates from the mean (±)

3. square deviation

4. calculate sample variance

5. square root

4 types of data plotting

• histogram

• box plot

• scatter plot

• data summary

histograms + 2 types

• no gaps between bars (continuous data)

• frequency: y = frequency density

• proportion: y = proportion of sample

box plots

• median, upper & lower hinge

• upper & lower hinges: value halfway between min/max value & the median

• h-spread

• upper & lower inner fences

• adjacent values

how to work out h-spread in box plots

upper hinge-lower hinge

how to work out upper & inner fences in box plots

upper/lower hinge - 1.5 * h-spread

what are adjacent values in box plots

the lowest & highest values that fit within the inner fences