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If you
have some free time this week, you might want to teach your
child how to create their own statistical tables and charts.
This practice can either be presented as a chore or a game,
but games seem to make their marks more quickly than forced
efforts. Then, when your child encounters this practice in
math class, she might become the star pupil.
While
some tables and graphs might seem complex, they usually begin
with what is known as a "frequency table." You will need graph
paper (larger graphs, like ?", are good), pencils with erasers,
a simple calculator, a ruler, and some crayons or markers.
Frequency
Table: Say that you make a list of all the investments
you made at BUYandHOLD during the twelve months in 2004 (start
with January) I'll keep the figures low for computing ease:
$9, $12,
$20, $20, $15, $9, $12, $10, $15, $20, $15, $9
The information
above is called "raw data," and it might be difficult for
you to decipher information from this format. But, if you
count the number of times - or frequency - that each dollar
amount appears, you can display the information like this:
| Investment |
Frequency |
| $9 |
3 |
| $10 |
1 |
| $12 |
2 |
| $15 |
3
|
| $20 |
3
|
| Total
|
12
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The chart
above represents a simple way to clarify information, where
the investment represents the category and the frequency equals
the number of times each category appears in the "data set."
The total number of frequencies (12) represents 100%. So,
if you want to know the "relative frequency" for a category
(or the frequency expressed in fractions or percentages),
then you would divide the investment frequency by the total
frequency. In other words, three out of twelve investments
cost $9, so:
- The
relative frequency for $9 investments equals 3/12 or 25%
- The
relative frequency for $10 investments equals 1/12, or 8.3%
- The
relative frequency for $12 investments equals 2/12, or 16.7%
- The
relative frequency for $15 investments equals 3/12, or 25%,
- The
relative frequency for $20 investments equals 3/12 or 25%
Now, notice
that the final percentages add up to 100%, but only because
I round up the 16.6666% to 16,7%. Actually, you can round
down the 8.3% to 8% and continue to round up the 16.7% to
17% to make this game a little easier. The next step involves
formulating a graph from these figures.
Simple
Graph: You can create a simple graph from the information
in the frequency chart. You need to create a table that looks
very similar to the charts shown at BUYandHOLD when you head
to Research
Stocks and click on one of the top ten holdings. First,
draw a box (on graph paper) where the twelve months are listed
along the bottom (Jan., Feb., Mar., etc.). Then list the prices
along the side, starting with "0" and increasing in increments
of five. That left-hand list would then read, "0 - 5 - 10
- 15 - 20."
Now, begin
under the "10" along the left side above January to make the
first dot, and continue to make dots above each month along
the prices that are represented by those months. While the
"10," "15," and "20" dollar amounts might be easy for the
kids to find, you may have to help them understand where the
"9," "12" stand. Now, just connect the dots, and they have
a graph that illustrates your investment amounts during 2004.
Bar
Chart: Make another box just like the one you made for
the graph above and follow the same instructions up to the
directions for connecting the dots. Now, however, instead
of connecting dots they will take a ruler and draw a straight
line from the month listed at the bottom up to the dot. Now,
they can take their crayons and make each line a different
color if they want.
Another
way to create the graph and bar charts incorporates the categories
(dollar amounts) along the bottom and the frequencies (number
of times the categories occurred, like "1" for the ten dollar
amount) along the left side. Remember to begin with "0" on
the left side. Since there are no more than 3 frequencies
for any given dollar amount, just number from 0 to 5 along
the left side. Then, repeat the exercises above but let the
kids try to keep track of the categories and frequencies without
your help. This is where the practice becomes both a game
and a skill.
Older
kids can add the relative frequency (percentages) vertically
along the right side of the bar chart. Then, they can analyze
whether their frequencies along the left side match their
relative frequencies along the right side. This type of chart
is very easy to read as long as the kids don't create drop-shadows,
3-D effects, or any other fancy graphics that would make the
visuals difficult to read. However, if they do get fancy
with their charts, make the point that their efforts make
great artwork, but they don't work as readable charts (for
helpful hints about this information, read
last week's article).
Have Fun!
Until
Next Week,
Linda Goin
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