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270 Chapter 16: Statistics and Data Plots
16STATS.DOC TI-89/TI-92 Plus: Statistics and Data Plots (English) Susan Gullord Revised: 02/23/01 1:12 PM Printed: 02/23/01 2:17 PM Page 270 of 22
In a data variable, you can use any column in the Data/Matrix Editor
to specify a frequency value (or weight) for the data points on each
row. A frequency value must be an integer
‚
0 if
Calculation Type =
OneVar
or
MedMed
or if
Plot Type = Box Plot
. For other statistical
calculations or plots, the frequency value can be any number
‚
0.
For example, suppose you enter a student’s test scores, where:
¦
The mid-semester exam is weighted twice as much as other tests.
¦
The final exam is weighted three times as much.
In the Data/Matrix Editor, you can enter the test scores and
frequency values in two columns.
To use frequency values, specify the frequency column when you
perform a statistical calculation or define a stat plot. For example:
In a data variable, you can use any column to specify a category (or
subset) value for the data points on each row. A category value can
be any number.
Using Frequencies and Categories
To manipulate the way in which data points are analyzed, you
can use frequency values and/or category values. Frequency
values let you “weight” particular data points. Category values
let you analyze a subset of the data points.
Example of a
Frequency Column
Tip: A frequency value of 0
effectively removes the data
point from analysis.
Note: You can also use
frequency values from a list
variable instead of a
column.
Example of a
Category Column
c1 c2
85 1
97 1
92 2
89 1
91 1
95 3
c1
85
97
92
92
89
91
95
95
95
Test scores
Frequency values
Frequency of 2
Frequency of 3
These
weighted scores
are equivalent to
the single column
of scores listed to
the right.
Set this to YES.
Type the column
number (or list
name) that
contains the
frequency values.