measures of central tendency and dispersion Flashcards
what are the 3 measure of central tendency
mean
median
mode
how do you carry out a mean
add up all of the values and divide by the number of values that you have
evaluate the usefulness of a mean
+ contains the whole data set so is representative of the data set as a whole
- any extreme scores will distort the data
what type of data is a mean used for
interval data (continous)
what is the mode
the most frequently occurring value
evaluate the usefulness of a mode
+ not influenced by extreme values
- crude measure may not represent the whole data set
what type of data is the mode used for
nominal data (discrete/categoric)
how do you find the median
middle values when all of the values are placed in rank order
evaluate the usefulness of the median
+ not influenced by extreme values
- can be distorted by small samples
- less sensitive (doesn’t use all of the data)
what type of data is the median used for
ordinal data
what are the 2 measures of dispersion
range
standard deviation
how do you carry out the range
highest value - lowest value +1
evaluate the usefulness of the range
+ easy to do
+ takes into account extremes of the data
- can be greatly influenced by just one score
- ignores all data but 2 points so doesn’t measure the general spread of data around the mean
explain standard deviation
calculates the average distance of all scores from the mean. shows whether scores in a condition are similar to each other or are more spread out
what does a small standard deviation mean
scores are clustered around the mean
