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Topic: Lack of Freq Calc (fwd)
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Bob Hayden

Posts: 2,384
Registered: 12/6/04
Lack of Freq Calc (fwd)
Posted: Sep 15, 1996 10:36 AM
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----- Forwarded message from -----

I noticed in Workshop Stats that the data files on disk have every data item
entered separately even when the data is given as tallies in the book (for
example in Activity 3-10 (d,e)). It is clear from previous emails that
dealing with frequency data is difficult with Minitab. However, it is very
easy to do on the TI-83 (stat calcs and plots all will handle frequencies).

----- End of forwarded message from -----

Each variable is a column and each row is a case is standard database
practice, not peculiar to Minitab or even statistical software. And
there is a reason for this. As soon as you have two variables

1 4
3 4
3 2

it is clear that you do NOT want to store this as

1 1 2 1
3 2 4 2

as that completely destroys the information on which x goes with which
y. It's the same problem as sorting your data one variable at a time
-- it completely scrambles your database.

If you START with data like this, you can still enter it into Minitab
just as easily as the TI-83 (check "set with patterned data" in the
index) but it will STORE it in standard database fromat. (Of course
it cannot restore the lost information.)

Because it handles variables in a consistent way, if I have 100
variables in Minitab, I can

describe c1-c100

and get (correct) summary statistics on every one. If I could store
100 variables in the TI-83, I'd have to go through them column by
column to determine which columns are actual data and which are
frequencies. If I don't, the calculator will STILL compute answers,
but they will be wrong for all data stored in the
"one-variable=2-columns" format. I think this is a "feature" of the
TI-83 that would be a nightmare if it were powerful enough to do real
data analysis. Fortunately, it is not.

| | Robert W. Hayden
| | Department of Mathematics
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| | Plymouth, New Hampshire 03264 USA
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