## What Has Changed?

In Ebola 2014, we looked at data from the CDC regarding Ebola cases and deaths. The data was plotted in an Excel spreadsheet and on a TI-83+ graphing calculator to determine the curve of best fit. At that time the function that described the data was an exponential growth model.

Over time, more clinics were mobilized, better burial practices were enforced and the graphs of the number of cases and deaths have changed.

To work with the more recent data, download Reported Ebola Cases and Deaths or download the csv file from the CDC’s website.

Right click on the B column to insert a new column. Add the column heading and in cell B2 add the formula **=A2-$A$2**. Change the format to **General**. Fill the formula down.

Add a column heading in cell **I1** for **Total Cases** and one in cell **J1** for **Total Deaths**. In cell **I2** type **=C2+E2+G2** to add the total cases for all countries and press Enter. Do the same for cell **J2** with the formula **=D2+F2+H2**. Fill the formulas down.

Highlight cells **B1** down to **B77**, then press the **Ctrl** key and highlight **I1** to **I77** to select discontiguous columns. Go to the **Insert** menu and choose **Scatter** and choose the first scatter chart listed.

Repeat the process using cells **B1 **to **B77** with **J1 to J77** to plot the total deaths.

## Obtaining a Curve of Best Fit

Because Excel can not calculate a logistics curve of best fit, if you want to generate an equation that fits the curve, you will need to enter the data into a TI graphing calculator.

Start by pressing **Stat > Edit** and pressing **Enter** to add the days since the outbreak began to the **L1** column and **Total Cases** to the **L2** column.

Next, press **STAT > CALC** and arrow down to **Logistics** then press **Enter**. Press **2nd** **1** (L1) **,** **2nd 2** (L2) then press **Enter**.

The equation will be generated and displayed on the screen.

Press the **Y=** button on the calculator. Type the equation into the **Y1** line.

Set up the stat plot by pressing the **2nd Y=**. Turn **Plot 1** **On** and make the mark a small dot.

Press the **Zoom** button and choose **9**. The data and curve will be displayed.

To better see when the curve is likely to flat line, see the logistics curve plotted on Desmos.

## Extensions

Use a graphing calculator to predict when no more deaths from this outbreak will occur by finding it’s logistics equation. Repeat the process for the individual countries listed in the data set.

For an example of another logistics curve see Logistics Growth Curve – AIDS Infections