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Spreadsheet and Graphing Exercise

Biology 210 – Introduction to Research

There are many good spreadsheet programs for analyzing data. We will go over one of these,

MS Excel. Below are a series of examples for you to follow and we will go through these to

show you how to work with the MicroSoft Excel spreadsheet and graphing program.

SAMPLE DATA:

Table 1 Age

(days)

Height of plants (in cm)

Plant 1 Plant 2 Plant 3 Plant 4

7 1.0 0.8 1.1 1.2

14 2.1 2.0 1.8 2.3

21 4.0 4.3 3.6 4.1

28 6.2 6.0 5.0 6.2

35 9.0 9.2 7.5 9.3

42 11.5 11.3 9.1 11.0

Table 1. Example Control Data for Fast Plant Growth Experiment. These control plants were

grown under 24 hour lighting conditions and watered with tap water. Plants from each pot were

identified and measured weekly. Measurements were taken from the soil to the end of the end of

the main stem of each plant.

Table 2 Age

(days)

Height of plants (in cm)

Plant 1 Plant 2 Plant 3 Plant 4

7 1.0 0.8 1.1 1.2

14 2.1 2.0 1.8 2.3

21 3.0 3.3 3.2 3.1

28 4.2 4.0 4.5 4.2

35 5.0 5.2 5.1 5.3

42 6.5 6.3 6.1 6.0

Table 2. Example Experimental Data for Fast Plant Experiment. These control plants were

grown under 8 hour lighting conditions and watered with tap water. Plants from each pot were

identified and measured weekly. Measurements were taken from the soil to the end of the end of

the main stem of each plant.

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Inserting Functions in an Excel Spreadsheet

After you have entered your data in a spreadsheet, you should calculate both the

‘Average’ (also called the Mean) and ‘Standard Deviation’ for your control and

experimental plant data.

In your Excel spreadsheet, choose the cell where the functional value will be entered (in

the example below it will be entered in cell ‘G4’ for average).

Choose the fx button on the Excel scroll bar. The = sign will appear in G4, the select

‘Statistical’ as your category and then scroll down to ‘Average’ in the Statistical Function

category.

Highlight the values that you want to be calculated in the average or standard deviation.

(You may need to move the Function window to see the cells that you will highlight.

(Note that you do NOT want to include the Age Column – everything below A3 – in this

calculation.)

Be sure you know how to select cells – you will use this same method of cell selection as

you prepare a graph using Excel. In this example we would like to take the Average of

cells B4 to E4.

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Excel has cut and paste Functions to fill the remaining cells in the Average Column on

the spreadsheet. This eliminates the need for you to select each individual row for each

functional calculation. Excel automatically shifts the cells to used in each function.

Now repeat for Standard Deviation and for both data sets.

Using Excel to Prepare a Graph

Step 1 of 4: Chart Type

Choose the graph wizard which you would like to use. Go to the Insert tab. For these

data it is best to use a line graph format. Click on the first line graph type in the second

row. Our selected graph is a ‘Line graph with markers displayed at each data value.’

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Step 2 of 4: Chart Source Data

Go to Select Data at the top of the menu. Then highlight all of the plant growth data for

the control group (cells B4 to E9). These data will be placed on the Y-axis of your plot.

You may select the data for all four individual plants and Excel will automatically draw

four different lines for each of these four ‘series’ of data. You should automatically see

what the graph will look like.

Note that the data for each plant is labeled ‘Series 1’, etc. At this point you must rename

your legends for the figure (Series labels). In the Select Data Source Window, highlight

Series 1, hit the Edit button and change the name to Plant 1. Repeat for each Series.

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Now you need to correct the X axis values. Again in the Select Data Source window,

select ‘Horizontal (Category) Axis Labels and click Edit. Then a new window will open

up ‘Axis Labels’ – now highlight the Age values (cells A4 – A9) to get the correct age in

days displayed.

Step 3 of 4: Chart Options

Now it is time to clean up the Figure. You may click on the chart and its various parts to edit

those items.

Click on the horizontal gridlines to edit them. Hit ‘Delete’ to remove the grid lines for a

cleaner look.

Click on the X-axis. Open the Format Axis window. Go to Position Axis and select On

Tick Marks.

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To add Axis Titles – Click on the Chart which opens the chart edit windows. Go to

Layout and Click on Axis Titles. Add Primary Horizontal Axis Title and Primary

Vertical Axis Title.

Also add a chart title using the same Layout window.

Click on the Chart, go to Design and then to the Move Chart button to save it to a new

sheet. Be sure to give it a good name.

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Adding Error Bars to Your Graph

Prepare a graph of the average height at each (instead of the height of each individual

plant) by selecting the ‘Average’ column for the control plants in your spreadsheet

(instead of the four individual plant columns). On this type of graph it is often a good

idea to include error bars to give an idea of the variability in the data that were used to

calculate the graph. You may use standard deviation, standard errors or 95% confidence

internals. We will use the standard deviations we calculated for the average height data.

After preparing a graph of the average heights, click on the graph to open the chart

editing menu bar. Then go to Chart Tools and the Layout Tab. Select the Error Bars

button.

When the Error Bars scroll appears, to the bottom to select More Error Bar Options.

When the Format Error Bars window opens up, select Custom Error bars (bottom of the

window).

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After selecting Custom Error Bars, select Specify Value.

You may have to move the windows around to see your data. To select your StanDev

data, select Positive Error Value, click on the table symbol in that line, a new window

will open up, then highlight the StanDev data (Cells H4 – H9).

Repeat for Negative Error Value.

Go to Design under the Chart Tools and save to another sheet.

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Now for your assignment: Prepare a graph for the Experimental Plant Heights

showing individual plant data.

Prepare another graph showing both the Control Plant Mean Height and the

Experimental Plant Mean Height with the proper Error Bars. You will need to group

the Average data together in order to put the new graph showing both plant

experiments together.