1.2 - displaying quantitative data with graphs
DESCRIPTION
1.2 - Displaying quantitative data with graphs. (Histograms). Histograms. The most common graph of quantitative data. Classes: the intervals along the bottom axis. These need to be of equal width Frequency: the count of individuals of a class occurring - PowerPoint PPT PresentationTRANSCRIPT
1.2 - Displaying quantitative data with
graphs(Histograms)
HistogramsThe most common graph of quantitative data.
Classes: the intervals along the bottom axis. These need to be of equal width
Frequency: the count of individuals of a class occurring
Relative frequency: the percent of the individuals in a class
(this is more useful, especially when you are comparing two sets of data with an unequal total
of individuals)
Construct 2 histograms.One displaying the frequency and one
displaying the relative frequency.
The following table presents the average points scored per game (PTSG) for the 30
NBA teams in the 2009-2010 regular season.
101.7 99.2 95.3 97.5 102.1 102
106.5 94 108.8 102.4 100.8 95.7
101.7 102.5 96.5 97.7 98.2 92.4
100.2 102.1 101.5 102.8 97.7 110.2
98.1 100 101.4 104.1 104.2 96.2
Steps for constructing a histogram
1st - divide the range of data into class of equal width.
2nd - find the count and percent of individuals in each class.
3rd - label and scale your axes
4th - draw your histogram
1st stepWhat is the range of our data?
What would be a good class size to choose?
What are the classes?
2nd StepFill in a frequency table and a relative frequency
table.Frequency
TableClass Count
Relative Frequency Table
Class Percent
3rd step
PTSG
Frequ
en
cy
PTSGR
ela
tive F
req
uen
cy
4th step
PTSG
Frequ
en
cy
PTSGR
ela
tive F
req
uen
cy
Describe the data of the average points per game in the 2009-2010 NBA
season.
Don’t forget your “SOCS!”The data
appears to be _______
with a peak of _____ .
The _____ appear to be any outliers.
The center of the data
occurs around ______
The histogram shows that
the percent of points per
games ranged from
__________
How does class size effect the shape of the
histogram?
www.whfreeman.com/tps4e
Last Pieces of advice about histograms
1. Don’t confuse histograms and bar graphsHistograms are for quantitative dataBar graphs are for categorical data
4. Just because a graph looks nice, doesn’t mean it’s necessarily a
meaningful display of data. (Excel is a terrible tool to use for
statistical graphs)
3. Use percents instead of counts when comparing distributions with different numbers of
observations.
2. Don’t use the counts or percents as the data. Use the data to find the counts and percents for your
graph.