Descriptive Statistics Flashcards
what are measures of tendency?
‘averages’ which give us information about the most typical values in a data set.
what are the 3 main types of measures of tendency/averages?
Mean
Median
Mode
how is the mean calculated?
calculated adding up all the scores or values in a data set and dividing this figure by the total number of scores there are.
what is the median?
the middle value in a data set when scores are arranged from lowest to highest. if even number of scores the median is halfway between the two middle scores.
what is the mode?
the most frequently occurring score/value within a data set. may be two modes (bi-modal) or no mode if all scores are different.
when there is an outlier in the data set what measure of central tendency is most appropriate?
mode or median
if there are no outliers, only a few repeated numbers and the numbers are similar then what measure of central tendency should be used?
mean
what are measures of dispersion?
based on the spread of scores: that is, how far scores vary and differ from one another.
what are the two main measures of dispersion?
Range
Standard Deviation (SD)
what is range?
a simple calculation of the spread of scores - worked out by taking away the lowest value from the highest value and (usually) adding 1.
what is standard deviation?
more sophisticated measure of dispersion - it is a single value that tells us how much scores deviate (move away from) the mean.
what does the larger the sd mean?
larger the SD, the greater the spread or dispersion within a set of data.
how to calculate the sd of a data set?
- calculate the mean
- complete table
- substitute figures back into the formula
- division
- square root
what is the formula for standard deviation?
