To add a Gaussian curve to a histogram in Excel, follow these steps:

1. Create your histogram in Excel by selecting your data and going to the "Insert" tab, then selecting "Histogram" from the "Charts" section.
2. Calculate the mean and standard deviation of your data set using the AVERAGE and STDEV functions in Excel.
   For example:
   - Mean:
   Code:

   =AVERAGE(A1:A10)

   - Standard deviation:
   Code:

   =STDEV(A1:A10)

3. Create a column of x-values for your Gaussian curve.
4. Use the NORMDIST function in Excel to calculate the y-values for your Gaussian curve.
   For example: If your mean is in cell B1 and your standard deviation is in cell B2, you could use the following formula to calculate the y-value for an x-value of 50:
   Code:

   =NORMDIST(50,B1,B2,TRUE)

5. Create a line chart from your x-values and y-values to display the Gaussian curve. Select your x-values and y-values, then go to the "Insert" tab and select "Line" from the "Charts" section. You may need to adjust the formatting of the chart to make it look the way you want.