research methods- measures of central tendency and dispersion Flashcards
what’s the mean?
add up all the scores and divide by the number of scores
evaluation of the mean
-sensitive measure
-may be unrepresentative
ao3 of mean: sensitive measure
-includes all the scores/values in the data set within the calculation
-represents the data better than the median or the mode
ao3 of mean: may be unrepresentative
-one very large or very small number makes it distorted
-median or mode tend not to be so easily distorted
what’s the median?
middle value, place scores in ascending order and select middle value
If there are two values in the middle, the mean of these is calculated.
evaluation of the median
+less affected by extreme scores
-less sensitive than the mean
ao3 of median: less affected by extreme scores
-median is only focused on the middle value
-some cases it may be more representative of the data set as a whole
ao3 of median: less sensitive than the mean
-actual values of lower and higher no.s are ignored
-extreme values Amy be important
what is the mode?
most frequent or common value, used with categorical/nominal data
evaluation of the mode
+relevant to categorical data
-an overly simple measure
ao3 of mode: relevant to categorical data
-when data is ‘discrete’ i.e. represented in categories
-sometimes the mode is the only appropriate measure
ao3 of mode: an overly simple measure
-mode may be at one extreme
-it’s not a useful way of describing data when there are many modes
what are the three measures of central tendency?
-mean
-median
-mode
what is the range?
the difference between highest to lowest value (sometimes 1 is added if values have been rounded up or down)
evaluation of range
+easy to calculate
-doesn’t account for the distribution of the scores
ao3 of the range: easy to calculate
-arrange values in order and subtract largest from smallest
-simple formula, easier than the standard deviation
ao3 of the range: doesn’t account for the distribution of the scores
-range doesn’t indicate whether most numbers are closely grouped around the mean or spread out evenly
-standard deviation is much bettie measure of dispersion in this respect
what is standard deviation?
measure of the average spread around the mean. The larger the standard deviation, the more spread out the data is
evaluation of standard deviation
+more precise than the range
-may be misleading
ao3 of standard deviation: more precise than the range
-includes all values within the calculation
-therefore more accurate picture of the overall distribution of data set
ao3 of standard deviation: it may be misleading
-can be distorted by extreme values
-also, extreme values may not be revealed unlike with the range
what are the two measures of dispersion?
-range
-standard deviation
