11.3 Graphing the Normal Distribution

The NORM.DIST(x,mean,standard_dev,FALSE) function calculates the normal probability density function that can be used to plot the bell-shaped curve. To graph the normal curve, we need x and y values. The x values correspond to the birthweights. The y values are values of the probability density functions.

First, you will generate the y-values and then use a scatter plot to display the bell-shaped curve.

  1. Select the cell K1 and type the label Y-Values.
  2. Below Y-Values, enter the formula = NORM.DIST(J2,$H$2,$H$4, FALSE).
  3. Select cell K2 and place the mouse pointer in the lower right corner of the selected cell until it becomes a + sign, and click-drag downward across the range that covers all the values in column K.

The y-values range from \(3.34\) x \(10^{-5}\) to \(1.71\) x \(10^{-4}\).

  1. Select all cells in the birthweight and Y-Values columns (select the first cells in columns J and K, then press the Shift + Arrow Down keys to select the whole range of data).
  2. Click Insert > Scatter > Scatter with Smooth Lines.
A screenshot of the normal curve generated.

Figure 11.1: The normal curve created.

The resulting graph needed to be adjusted (Figure 11.1 ). Use the instructions in Steps 3-8 in Section 9.2 Creating a Scatter Plot to make the necessary adjustments to the graph. Adjust the title, axis titles, and horizontal axis.