descriptive statistics Flashcards
measures of central tendency
inform us about central values for a set of data
average can be calculated in different ways, different situations
how to calculate the mean?
add up data items and divide by number of data items
advantages of mean
- representative of all data
- sensitive statistic - takes account of the exact distance between all values of all data
disadvantages of mean
- cannot be used with nominal data
- anomalous values can distort and misrepresent data
how to calculate median?
arrange in order of size and select the central value
even no. - calculate median value must add 2 median values and divide by 2
advantages of median
- easy to calculate
- not distorted by anomalies
- not affected by extreme scores so can be useful under such circumstances
disadvantages of median
- less sensitive than the mean because the exact values are not reflected
how to calculate mode?
most common value
advantages of mode
- unaffected by extreme values
- useful for discrete data
- can be used for nominal data
disadvantages of mode
- mode may not represent data
- data cannot be described using this statistic
measures of dispersion
finds how spread out data items are
how is range calculated?
(biggest value - smallest value) +1
advantages of range
- easy to calculate
disadvantages of range
- effected by extreme values
- doesn’t take into account the distribution of numbers
how is standard deviation calculated?
σ = √[(∑(d’)2 /n) - (∑d’/n)2] × i
