Transcript 1-7 - Fort Thomas Independent Schools

1-7 Data and Spread
Big Idea
Two measures of the spread of a data
set are range and mean absolute deviation.
Range, the difference between the maximum and
minimum values (M – m) of a data set is often used
in statistical reports to explain the spread of a set
of data.
Another calculated number used to explain the
spread of a data set is mean standard deviation.
1) find the mean of the data set; 2) subtract the mean
from each value; 3) find the absolute value of the
differences; and finally 4) find the mean of the absolute
values.
To find the mean absolute deviation with a graphing calculator.
5,11,3,6,9,4,0,15,6,8,11,7,2,1,3,4,10,9,4,6,8,0
Go to List, type in the data set in L1.
To find the mean of a data set, find the sum of the
data items then divide by the total # of items by:
1. Leave List (2nd, quit).
2. Then click 2nd key, catalog (above prgm), scroll
down to mean( , enter.
4. Click 2nd , List select L1, enter, enter.
To subtract the mean from each data set value:
1. Go to List, arrow up to L2 at the very top
2. Click 2nd List, select L1, enter
3. Type – mean #, enter
To find the absolute value of each #:
1. Go to List, arrow up to L3
2. Then click 2nd key, catalog (above prgm), scroll
down to abs( , enter
3. Click 2nd List, select L2, enter, enter
Find the mean the same as before, this time for L3
You have just found the mean absolute deviation.
Instead of using the letter m to represent the mean,
you will often see the symbol μ (mew) because
M represents maximum value and m, minimum.
Types of displays for data used often are frequency
tables, bar graphs and dot plots. You need to be
familiar with each type. See page 47 in your book.
The outlining shape of the plotted data can add
meaning to the data set. Here are some examples
with their names.
symmetric
uniform
skewed right
skewed left
Using excel spreadsheet to find M.A.D.
Data: 5,11,3,6,9,4,0,15,6,8,11,7,2,1,3,4,10,9,4,6,8,0
1. Type headings for columns in rows 1 and 2.
2. Type in your data values in column A.
3. Cell 26 type =, then go to box above column A, select average.
A dialog box will show you what you are averaging, so click ok and
6 will appear in cell A26
4. Select cell B3, type =A3-6, enter, -1 will appear in cell B3. To do the
other cells in B, click on B3 again and copy it. Then highlight the
cells B4-B24 (click and drag mouse), then enter. Column
B should now be filled with values.
5. Select cell C3, type =, go to the box next to average ▼ click to
pull down the menu. Select abs (absolute value), in the dialog
box type B3 then click ok. 1 will appear in cell C3. To complete the
column, select C3, copy, highlight cells C4-C24, enter.
6. Finally go to C26 to calculate the final average. Type =, go to box
▼ to pull down the menu of options, select average, click ok in
the dialog box. Your average should be 3.09 repeating.