MEASURES of SPREAD
(Using the Graphing Calculator)
A random survey of people at a science-fiction convention asked
them how many times they had seen STAR WARS. The results
are shown below:
3
6
4
3
2
4
8
9
10
12
5
3
1
30
15
2
5
10
16
7
Determine the mean, median, standard deviation, the first and third quartiles, the
interquartile and semi-interquartile ranges, and sketch the box-and-whisker plot.
STEP 1:
1.
2.
3.
STEP 2:
1.
2.
3.
4.
STEP 3:
1.
2.
3.
4.
5.
6.
7.
CLEAR ALL LISTS
Select 2nd MEM
Select 4:ClrAllLists ENTER (screen should say DONE)
Clear screen by selecting CLEAR
ENTERING DATA
Select STAT
Select 1:Edit (screen should show lists L1, L2, etc.)
Enter data in L1 by keying in number and selecting ENTER
after each value.
Select 2nd QUIT after the last value has been entered.
CALCULATE MEASURES OF SPREAD
Select STAT
Use arrow to select CALC
Select 1:1-Var Stats (screen should say 1-Var Stats)
Select 2nd L1 (screen should say 1-Var Stats L1)
Select ENTER (screen should display stats)
Use the arrow to move up and down the list of stats.
State the following values:
i)
mean ( x )
____________
ii)
median
____________
iii)
standard deviation (s)
____________
iv)
first quartile (Q1)
____________
v)
third quartile (Q3)
____________
vi)
interquartile range (Q3 – Q1)
____________
vii)
semi-interquartile range
____________
STEP 4:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
DRAW THE BOX-AND-WHISKER PLOT
Clear the screen using CLEAR
Select WINDOW
Enter the following values: Xmin
0
Xmax
35
Xscl
5
Ymin
0
Ymax
5
Yscl
1
Xres
1
nd
Select 2 QUIT
Select 2nd STAT PLOT
Select 1:Plot1
Select ON (use arrow and ENTER)
Select Type: box-and-whisker icon (use arrow and ENTER)
Select 2nd QUIT
Select GRAPH
Sketch the box-and-whisker plot below, labeling key values.
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