Descriptive statistics
Statistics that describe or summarise data collected from PPS e.g. use of graphs, tables,
central tendencies and measures of dispersions.
Measures of central tendency - are averages: mean, median and mode
Mean - add up all the data items and divide by the number of data items.
STRENGTHS
Representative - takes all values into account.
LIMITATIONS
Unrepresentative - if there are extreme scores, the mean becomes distorted
Median - rearrange the list from low to high. The middle score is the median. If there are two
middle values then add them up and divide by two.
STRENGTHS
Not affected by extreme scores
LIMITATIONS
Only middle value included - not all values taken into account
Mode - most common value in the list as well as two modes (bi-modal).
STRENGTHS
Not affected by extreme scores
LIMITATIONS
Can only be used if data is in categories
Measures of central tendency linked to levels of measurement:
Mode → Nominal data
Median → Ordinal
Mean → Interval
Statistics that describe or summarise data collected from PPS e.g. use of graphs, tables,
central tendencies and measures of dispersions.
Measures of central tendency - are averages: mean, median and mode
Mean - add up all the data items and divide by the number of data items.
STRENGTHS
Representative - takes all values into account.
LIMITATIONS
Unrepresentative - if there are extreme scores, the mean becomes distorted
Median - rearrange the list from low to high. The middle score is the median. If there are two
middle values then add them up and divide by two.
STRENGTHS
Not affected by extreme scores
LIMITATIONS
Only middle value included - not all values taken into account
Mode - most common value in the list as well as two modes (bi-modal).
STRENGTHS
Not affected by extreme scores
LIMITATIONS
Can only be used if data is in categories
Measures of central tendency linked to levels of measurement:
Mode → Nominal data
Median → Ordinal
Mean → Interval
