Chapter 3 - Descriptive Statistics Flashcards
what is ungrouped data
ungrouped data is raw data that has not been organised into groups or classes
what is grouped data
grouped data is data that has been organised into groups or classes
is grouped data still raw data?
no. grouped data has been subject to some data analysis such that it is no longer raw data
what is mode
mode is the item which occurs the most frequently
what is mean also knowned as
average
what is the formula for mean [ for ungrouped data]
mean = sum of all values/ number of values
what is median
the median is the middle value, which divides the set into two equal groups
what is the formula for finding median
if N is the number of values in a data set,
Median = [N + 1]/2 items
what is the measure if dispersion
the degree if variation in a data set identifies the spread of data from the mean value of the data set
what is range
range is simply the difference between the largest value and the smallest value in a data set
what is Interquartile Range
Interquartile range = Upper Quartile - Lower Quartile [ Q3 - Q1]
this covers the middle 50% of the observations
what is quartile deviation
quartile deviation is the average of the differences of the quartiles from the median
what is the formula for quartile deviation
[Q3 - Q1]/2
what is mean deviation
mean deviation is the difference between observations and the mean
what is the formula to find mean deviation
mean deviation =
step 1 Find the Mean
step 2 Find the Absolute Deviations
[ variable number - mean]
step 3 Find the Mean Deviation
[ Absolute Deviation]/ number of values
what is the most common measure of dispersion
standard deviation
what is the formula to find standard deviation
jus calc
how to find the coefficient of variation
standard deviation/ mean = s/x
how to find coefficient of variation [ as a percentage]
standard deviation/ mean x 100 = s/x x 100
how to find the median using the grouped frequency distribution
median: when cumulative frequency = n/2
[when n is large]
how to find the lower quartile using graphical method
Lower Quartile: when cumulative frequency = n/4 [ when n is large]
how to find upper quartile using graphical method
Upper Quartile: when cumulative frequency = 3n/4 [ when n is large]
how to find median using calculation method
Median: when cumulative frequency = n/2 [ when n is large]
