MI 3 Light Intensity Lab
Name __________________________
Excel (Office 2007) Instructions for the Light Intensity Lab
Using Formulas for the ln function:
Let’s assume you used column A for the distance data, column B for the adjusted intensity data.
Also let’s assume you used row 1 for your column labels (distance, adjusted intensity) and your
actual data begins in row 2.
Use column D for Ln(distance) and Column E for Ln(intensity). For column D, enter the
following Excel formula into cell D2:
=ln(A2)
Then, copy this formula down this column for all of your distance data. Repeat for the adjusted
intensity data.
Chart (graph)
1. Highlight the data to be graphed using the mouse. Note! To select non-adjacent columns
hold down the CTRL key while you use the mouse to select the data.
2. Click on the scatter plot icon under the Insert menu.
3. To generate the line of best fit, highlight your scatterplot then click on “trendline” under the
Layout menu. Choose “more trendline options” to open a window where you can choose to
display the trendline equation and/or the R 2 value.
4. To make a graph using a curve instead of blocks (markers) double click on any marker on the
graph. Then click on Change Chart Type (upper left corner of screen), and choose the icon
that shows curves with no markers. Your graph will show up as a curve instead of markers.
5. To add a title, labels for each axis, or change the legend: Highlight your scatterplot, then
click on the Layout menu, and select the appropriate “labels” icon.
Residual formula
To create a column of residuals for the adjusted intensity data vs. your model, type the following
into a cell to the right of the model column (assuming the log of your data is in column E and
your model is in column G):
=E2-G2
Then copy this formula down this column for all the data.
Excel 07
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MI 3 Light Intensity Lab
Name __________________________
Sum of squares of the Residuals
You will find it handy to square each residual and then sum these squared residuals. This
statistic is useful to evaluate the overall quality of each model. To create this statistic, you need
to type the formula that squares the residual in the cell to the right of the residual column. If
your residuals are in column H, then type:
=H2^2
Then copy this formula down this column for all the data. Then to sum all of these squares, type
in a cell below the last residual something similar to the following:
=SUM(H2:H10)
The H2:H10 should reference the cell of the top and bottom of the column of squared residuals.
You can also use the mouse to select this data range.
Using Formulas for the exponential function:
This is best described by using an example. We will construct the formula for
e
( .976  1.9* d )
Let’s assume you used column A for the distance data.
Use column G for the exponential expression above and enter the following Excel formula into
cell G2:
= exp(-.976-1.9*A2)
Then copy this formula down this column for all your distance data.
Using Formulas for a power function:
This is best described by using an example. We will construct the formula for
.215d
(-1.87)
Let’s assume you used column A for the distance data.
Use column J for the power function expression above and enter the following Excel formula
into cell J2:
= .215*A2^-1.87
Then copy this formula down this column for all your distance data.
Saving Your Excel File
Make sure you select SAVE AS from the file menu and then in the SAVE AS TYPE list of
options, select Microsoft Excel Workbook which should be at the top of the list. Type in a file
name and click on SAVE.
Excel 07
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