biostats measure of central tendency

skewness

absence of symmetry extreme values in one side distribution

measures of central location

aka measures of central tendency

normality testing

measures of shapes

negative symmetric positive

types of skews

mean

aka average, most popular and well known measure of central tendency; can be use with both discrete and continuous data, includes every value of data set as part of calculations

variance

another method for calculating the deviation of a group of scores from the mean

continuous data not significantly skewed or has outliers

appropriate for standard deviation

leptokurtic mesokurtic platykurtic

classification of kurtosis

measures of relative variation always a percent shows a variation relative to men used to compare 2 or more group

coefficient of variation

range

difference bet largest and smallest scores

platykurtic

flat and spread

cv=s/xX100%

formula coefficient for s.d.

cv=o/xX100%

formula coefficient populaton dev

x=Ex/n

formula of mean

XL-XS

formula range

E(x-xbar)2/n-1

formula variance

leptokurtic

high and thin distribution

particularly susceptible to the influence of outliers

mean has one disadvantage

standard deviation

measures of spread score within a set of data measures how concentrated the data around the mean

median

middle score set of data that has been arranged in order of magnitude (lowest to highest), lest affected by outliers and skewed data

mode

most frequent score in out data set; wish to know which is the most common category

ordinal

msct is median

nominal

msct is mode

interval not skewed

msct mean

interval skewed

msct median

mesokurtic

normal

measures of spread

other term for measures of dispersion describe variety in a sample or population use conjunction with the measures of central tendency

kurtosis

peakedness of distribution

two or more values share highest frequency most common mark is far away from the rest of the data on the data set

problems when using mode

depends on only 2 scores of data set two very different sets of data

range is rarely used in scientific work as it is fairly insensitive

ordinal data presenting results to people with little knowledge of statistics

range to use when

/E(x-xbar)2/n-1

s.d. formula

measures of central tendency

single value that attempts to describe a set of data by identifying the central position within the set of data