The first data set is the following list:
We will use the GNRND4 program on the calcualtor to generate this same data.
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We start the GNRND4 program and give it the two key values shown in Figure 1.
Then we press ![]() | ||||||||||||||
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The same data that we have in the table above now appears in the the list shown by the program
After looking at the list we press ![]() | ||||||||||||||
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We want to do a one variable analysis on this data. The command to do that is in the
STAT menu. We press ![]() ![]() ![]() | ||||||||||||||
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This pastes the command onto the main screen. We
press ![]() | ||||||||||||||
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Here is the first set of computed results. We see that
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In Figure 6 we still see the n=29 line, but now we see an additional
5 lines of information, namely,
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Although we just found all of these interesting values related to our original list of values,
we would like to get a picture or two of the values, a picture that helps us see how these values are spread out and how thaey may be clustered.
To do this we press ![]() ![]()
We note here that Plot1 is On and it is set
to produce a histogram (since
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We can leave Figure 7 and move to this menu by pressing the
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Figure 9 shows this histogram. | ||||||||||||||
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Press ![]() From the display we can see that the first "class" of values has a lower limit of 24 and an upper limit of 24.666667. One immediate consequence of this is that we now know the class width is 2/3. Furthermore, thre were 3 values in the original list that fell into this class. Knowing, as we do, that all of the values in the original list were integers we can conclude that the values 26 appears three times in the list. | ||||||||||||||
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We use the ![]() | ||||||||||||||
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We use the ![]() Looking ahead, the next class will have a lower limit of 26 and an upper limit of 26.666667. Our 10 instances of 26 will all fall into that class. | ||||||||||||||
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It would seem that a change in the WINDOW
settings would improve the usefulness of the historgrm.
We press ![]() THe settings shown in Figure 13 correspond to the values determined by the calculator when we used the ZoomStat command between FIgures 8 and 9. | ||||||||||||||
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The values that we have enterd to change the display to that shown in Figure 14 will
give us columns that are 1 unit wide with the column center being the integer values that appear in
the original list. That way each column will correspond to a single
integer value from our original list.
Once we have made these changes we press | ||||||||||||||
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Here is the redrawn histogram. Note that tehre are five classes. These correspond to the five different values that appear in our list, 24, 25, 26, 27, and 28. (Remember that we knew the range of values from the output of the 1-Var Stats command shown in Figure 6. | ||||||||||||||
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Againm, we can move to TRACE mode by pressing teh
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We move to the next class, the one that contains the value 26, and we are pleased to see that the calcultor reports that there were 10 such values in the original list. | ||||||||||||||
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An alternative to this kind of analysis is to use the COLLATE2
program. That program is designed to process even a long list of values,
as long as there are just a small number of different values in the list.
For Figure 18 we have started the COLLATE2 program
and we have given it the location of our list of values.
We will press | ||||||||||||||
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The initial output of the program tells us that there were 29 values in the list
but that there were only 5 different values. The approximate mean of the original values is
26.2414. The approximate standard deviation of the values,
treated as a sample, is 1.2146, whereas, the approximate mean of the values, treated as a
popultion, is 1.1935. We press ![]() | ||||||||||||||
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The program goes on to display the five quartile points. In addition, COLLATE2 displays the mode value of the original data, in this case it is 26. The display output of COLLATE2 is not much different from that of the built-in 1-Var Stats command that we saw in Figures 5 and 6. One difference is that the 1-Var Stats command displays many more significant digits for the computed values. A second is that COLLATE2 provides the number of distinct values found as well as the mode of the data. A third difference is that COLLATE2 creates six other useful lists that we can inspect, as well as setting the StatEditor to display those lists. | ||||||||||||||
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We use ![]() ![]() | ||||||||||||||
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The StatEditor opens showing the values in three lists, along with
the name of each list. The highlight is on the first item in the first list.
The name and index of that item is shown at the bottom of the page along with the value
that is in that indexed position of that list. Each row of data, i.e., each of the list items with a the same index number, is associated with the value shown in the ITEM list. Thus, reading across the first data line in Figure 43, we see that the first ITEM is 24, that 3 of the values in L1 are 24's, and that those 3 values represent 0.10345 (i.e., 10.345%) of the combined 29 values. The following table gives the names and intended use of the lists produced by COLLATE2.
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We use ![]() |
Thus far we have taken a list of values that we produced by GNRND4 in L1 and we have looked at that list of values in a number of different ways. Using COLLATE2, as demonstrated above, gives us not only the displayed values of Figures 19 and 20, but also the six computed lists shown in Figures 21 and 22. Of those lists, the first two, ITEM and ICNT provide us with all the information that we need to reconstruct the original list, although not in the origianl order of values. Thus, from looking at ITEM and ICNT that we need three 24's, four 25's, ten 26's, seven 27's, and five 28's. This view of the values in a list, where we specify both each distinct value and its corresponding frequency, is a grouped data view. Our next task is to see how the calculator can deal with such grouped data. Fortunately, we already have an example of this in ITEM and ICNT.
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First, we will return to the 1-Var Stats
command. When we give that command by itself it automatically assumes that we
want it to use the values in L1.
However, we can actually specify not only
the location of the data to use, but also the location of a corresponding
list of frequencies for that list of values. In this case, we want to
form the command
To start doing this we safely left Figure 24 via |
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We use ![]() ![]() ![]() ![]() |
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We have pasted the desired list name, LITEM,
onto the command, and followed that by pressing the
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We use ![]() ![]() ![]() |
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This completes the command. We will ask the calculator to
perform a 1-Var Stats command on data specified
by the distinct values in LITEM
and their corresponding frequency of appearance as given in
LICNT. Now we press
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This first page of output is identical to that produced above, in Figure 5, as well it should be. |
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When we scroll down to see the values in Figure 30 we see that they are the same as those in Figure 6. |
Figures 24 through 30 demonstrate the expanded use of the 1-Var Stats command. Let us do this again, but this time with some new data. We have been given the assignment of finding and displaying various attributes of the following data:
Data Value | Frequency |
35 | 8 |
14 | 2 |
53 | 1 |
27 | 9 |
22 | 7 |
61 | 2 |
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First, let us clear and set up the calculator.
We use ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
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Open the editor via ![]() ![]() |
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We start entering the data for our task. We will do this moving down the
first column, pressing the ![]() |
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Then, press ![]() |
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We return to the STAT menu via the ![]() ![]() ![]() |
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This places the command on the main screen.
Now, in our haste, we press |
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The results are shown in Figure 37. Something is terribly wrong!
For one thing, we know that we have many more that 6 values. In fact,
we know that we have exactly six distinct values, one of which, 27, appears
9 times. What have we done wrong?
The mistake is that we jsut issued the 1-Var Stats command. We never told the calculator to sue the frequencies that we carefully placed into L2. Before we correct this error, we will page down to see the rest of the output. |
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The 1-Var Stats command that we had the calculator perform produces all of this output. It is important to note that the calculator merely follwos our commands. It is up to us to verify that the results at least seem correct. In this case we know that we have made an error. |
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To produce the desired command,
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
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This is much better. We see results that are much more reasonable. |
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Here we scroll down to see the rest of the sults produced by 1-Var Stats. |
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Now we would like to get a picture of this data.
We will start with a histogram. To do this we check the
STAT PLOTS menu by pressing ![]() ![]() ![]() |
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Here we have already used the cursor keys to move to the
Type: selections and we have moved to the
histogram choice, ![]() ![]() ![]() |
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We move to that setting, press
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This is an interesting histogram, but it might help us to see
a bit more detail. Therefore, we move to TRACE mode via the
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In TRACE mode we see that the first column represents all of the values that are 14 or more and less than 21.833333. In our data that is just the 2 instances of the value 14. |
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Moving one column to the right, we see that there are 16 instances of values greater than or equal to 21.833333 and less than 29.666667. Looking back at the rel data we see that this class (column) represents the combined seven 22's and nine 27's. |
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Moving even further to the right we do see that there are no values in the class greater than or equal to 37.5 and less than 45.333333. |
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The historgram that the calculator created using the WINDOW
values that were set by the ZoomStatcommand is not particularly convenient.
In particular, that histogram has 7 "classes" but only 5 of them show any data.
This seems to be a little misleading in that we know that we have 6 distinct values in our data set.
With a little planning and even a bit of experimentation, we expect that the values that we have placed into the WINDOW settings shown in Figure 46a will produce a slightly better graph. |
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Press ![]() ![]() |
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Now we see that there are 2 instances of values greater than or equal to 9 but less than 16. |
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Moving to the right twice, that column represents the 9 values greater than or equal to
23 and less than 30. This histogram is a slight improvement in that we now have 6 classes (columns) that have data in them, corresponding to the 6 distinct values in our data. However, we are still missing the spread of the data because our class width is so large tht we do not see the breaks between most of the data. |
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Here are new WINDOW settigns that make an attempt to give an even better picture of the original data. making the Xscl value be 2 will increase our number of classes but it will also show the separation of the distinct values that we do have. |
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In this historgram we have a more accurate representation of the data and the spread
of the data. THinking aboutt he changes that we made in the WINDOW settings, we might be tempted to return to those and change the Xscl value to be 1. That way we would have separate classes (columns) even if we had distinct data values such as 14 and 15. Using the settings of Figure 46e these would have been combined into the first class. However, the calculator has a limitation that it will not do a histogram if it has more than 47 classes. With a class width of 1 we would need more than that many classes. |
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We can try another type of plot, a Box-and-whisker plot, to look at this
same data. We return to the Plot1 settings screen and
change the Type: to ![]() ![]() ![]() |
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This plot gives us a feeling for the spread of the data, showing us the quartile points and giving us a good feeling about the "middle" of the data. Seeing the long whisker on the right raises a concern about just how extreme the rightmost, the highest, values are. Perhaps it would have been better for us to have chose a modified Box-andWhisker plot. |
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We return to the Plot1 settings and choose the icon for
the modified Box-and-whisker plot,
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With teh modified Box-and-whisker plot we see that we have at least one outlier at the right side of the plot. We could return to the information of Figure 40a to see that Q3=35 and Q1=22. This gives the IQR= Q3–Q1=13. If we take 1.5*IQR we get 1.5*13=19.5. Going 19.5 above Q3 puts the upper limit at 35+19.5=54.5. Thus, our two instances of 61 can be considered outliers. |
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Moving into TRACE mode, via ![]() ![]() |
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Moving to the right one more time, we see that the value of the outlier is 61, although this plot does not tell us that such a value has two instances in our data set. |
©Roger M. Palay
Saline, MI 48176
September, 2012