Measures of Variation Flashcards
Measures of central location __ __ give an __ description of our data
do not give an adequate description of our data
Most important statistics for measuring the variability of a set of data
- range
- variance
the difference between the largest and smallest number in a set
range of a set of data
provides a method for converting observed variances to standard form so that they can be more easily understood and compared
standard deviation
provide the most powerful estimate of variation because they consider the value of each score
- standard deviation
- variance
- least reliable of the measures and is used only when one is in a hurry to get a measure of variability
- may be used for ordinal, interval, or ratio data
range
most important measures of variability
- standard deviation and its square,
- variance
average of the squared deviation around the mean
variance
- used whenever a distribution approximates a normal distribution
- basis for most statistics used in analysis of data
standard deviation
range may be used for
- ordinal data
- interval data
- ratio data
standard deviation is used with
- interval data
- ratio data
a graph or data set organized to show the frequency of occurrence of each possible outcome of a repeatable event observed many times
frequency distribution
data that are presented in the form of frequency distribution are called
grouped data
lowest and largest values that can fall in a class interval
class limits
number of observations falling in a particular class interval
class frequency
numerical difference between the upper and lower class boundaries of a class interval
class width
- midpoint of the class interval
- average of the class limits
class mark
- total frequency of all values less than the upper class boundary of a given class interval
- used to determine the number of observations that lie above (or below) a particular value in a data set
Cumulative frequency
plotting the class frequency against the class limits
bar chart
frequency against the class boundaries
frequency histogram
frequency against the class marks
frequency polygon
cumulative frequency against the upper class boundaries
cumulative frequency polygon or ogive
used when the median is used as an average; when the data depart noticeably from the normal
quartile deviation
quartile deviation is used for what data
ordinal data
quartile deviation Q is frequently called the
semi-interquartile range
