7.7 Statistics & StatisticalGraphs7.7 Statistics & StatisticalGraphs
p.445p.445
An intro to StatisticsAn intro to Statistics
•Statistics – numerical values used tosummarize & compare sets of data (suchas ERA in baseball).
•Measures of Central Tendency – mean,median, & mode are the 3 we will beusing. Tells you what the “center” of thedata is.
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Ex: Find the mean, median, & mode ofthe following set of numbers: 36, 39, 40,34, 48, 33, 25, 30, 37, 17, 42, 40, 24.Ex: Find the mean, median, & mode ofthe following set of numbers: 36, 39, 40,34, 48, 33, 25, 30, 37, 17, 42, 40, 24.
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Measures of DispersionMeasures of Dispersion – tell howspread out the data are.
* Range – Difference between thelargest and smallest values.
(for example: the range of the lastexample would be 48-17=31)
* Standard Deviation - (σ – “sigma”)
x1, x2, x3, …, xnare the entries inthe data set.
n is the number of entries in the set
x is the mean
Ex: Find the standard deviation of the datafrom the first example.
Box-and-whisker plotsBox-and-whisker plots
0 10 20 30 40 500 10 20 30 40 50
Minimumvalue (17)
Median(36)
Maximumvalue (48)
Lower Quartile –median of allnumbers in the listto the left of themedian
(25+30)/2 = 27.5
Upper Quartile –median of all numbersto the right of themedian
(40+40)/2 = 40
Box
Whisker
Whisker
Hints for making abox-and-whiskers plot:Hints for making abox-and-whiskers plot:
•Make sure data is in order from least togreatest.
•Find the minimum value, median,maximum value, upper & lower quartiles.
•Plot the points for this info below a numberline.
•Draw the box and whiskers.
Frequency DistributionFrequency Distribution
Title Goes Here
Interval
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Frequency
0 to 9
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10 to 19
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40 to 49
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Assign appropriateintervals that willinclude all datavalues in the set.
Put a tally markfor each datavalue in theappropriate row.
Count thenumber of tallymarks and putthe total in thelast column.
Another way to show the sameinfo. is in a histogram.Another way to show the sameinfo. is in a histogram.
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TITLE HERETITLE HERE
0 - 9
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20 - 29
30 - 39
40 - 49
LABEL HERELABEL HERE
LABELLABEL
HEREHERE
Intervals
Frequency
Bars should betouching!