How to Create a Normal Distribution Bell Curve in Excel
A bell curve is a symmetrical graph in statistics that depicts the tendency of data to cluster around a center value, or mean. Because Excel doesn’t have built-in solutions, you’ll have to plot it yourself. This tutorial will show you how to create a normal distribution bell curve in Excel.
Here’s how you might grade a class of 200 students on a curve, based on their relative performance to other students in the class as well as their ability to perform at the top of the class.
Step #1: Find the mean.
The mean is the average value of a sample or population of data. To calculate the average of the exam scores in the dataset, type the following formula into any empty cell (F1 in this example) next to your actual data (columns A and B).
Step #2: Find the standard deviation.
The formula calculates the standard deviation of all the values in the specified cell range (B2:B201), but don’t forget to round up the result.
Step #3: Set up the x-axis values for the curve.
A chart is made up of a large number of intervals (think of them as steps) that are joined together to form a smooth curve, with the x-axis representing a student’s exam score and the y-axis representing the probability of that student receiving that score on the exam.
Step #4: Compute the normal distribution values for every x-axis value.
To find the probability of receiving a specific exam score, type the formula into the first interval’s cells (E4) and copy it into the rest of the cells, locking the mean and SD values so that you can easily execute the formula for the remaining intervals.
Step #5: Create a scatter plot with smooth lines.
Go to the Insert tab, click the “Insert Scatter (X, Y) or Bubble Chart” button, and select “Scatter with Smooth Lines” from the helper table containing the x- and y-axis values (E4:F153).
Step #6: Set up the label table.
If you don’t have any data to describe the bell curve, let’s make the normal distribution more informative by adding labels illustrating all the standard deviation values below and above the mean (you could also use them to show the z-scores instead).
Step #7: Insert the label data into the chart.
Right-click on the chart plot and select ” Select Data. ” In the dialog box that appears, select ” Add. ” Highlight the respective cells ranges from the helper table for ” Series X values” and ” Series Y values.”
Step #8: Change the chart type of the label series.
To create a combo chart, go to the Combo tab and change the ” Chart Type ” for Series “Series2″ to ” Scatter. ” Make sure ” Series1 ” is not pushed to the Secondary Axis, as this can happen when you make a Combo.
Step #9: Modify the horizontal axis scale.
Adjust the horizontal axis scale to center the chart on the bell curve; you can adjust the axis scale range as needed. Since you know the standard deviation ranges, set the Bounds values a little away from each of your third standard deviations to show the curve’s “tail.”
Step #10: Insert and position the custom data labels.
You can now add custom data labels to your charts by right-clicking on any Series”Series2″ data label and selecting “Add Data Labels.” Under ” Label Position,” choose ” Above.” You can also remove the gridlines from your chart by right-clicking on any Series”Series2″ data label and selecting ” Remove Gridlines.”
Step #11: Recolor the data markers (optional).
You can also remove the borders around the dots if you don’t want them to show by right-clicking on any Series”Series2″ data label.
Step #12: Add vertical lines (optional).
You can add vertical lines to the chart as a final adjustment to help emphasize the SD values. You can now create a normal distribution bell curve from any dataset using these simple steps. Download our free Normal Distribution Bell Curve Template for Excel to assist you with this task.
How do you make a bell curve?
What Is a Bell Curve Graph and How Do I Make One?
- Calculate Sample Average. Calculate your sample mean.
- Determine Standard Deviation. Determine your standard deviation to see how far each score deviates from the average.
- Plot Data. Plot your mean along the x-axis.
- Draw the Graph.
How do I plot a curve in Excel?
To generate a curved graph in Excel, select Insert to open a window of options, then Charts to open the chart and graph options. Click on XY Scatter to open a window of options to setup the final graph.
How do you read a bell curve?
Examine the symmetrical shape of a bell curve. The largest portion of scores should fall in the center, while the smallest areas to the far left and right should contain the very lowest and highest scores. Read across the curve from left to right.
What is a bell curve grading system?
Grading on a curve, also known as bell curving, is a grading method in which students’ grades are distributed over a normal distribution, resulting in a majority of students receiving a grade that is close to the average.
Can a bell curve lower your grade?
Grading on the bell curve system can and does have an impact on grades; it can lower or improve student grades, standardize grades across instructors, and prevent grade inflation; it can also motivate students, identify students for alternative programs, and allow for the use of outside test models.
How do I make a bell curve in Word?
Make a curve.
- Click Shapes on the Insert tab, then Lines, then Curve.
- Click where you want the curve to start, drag to draw, and then click wherever you want to add a curve.
- To end a shape, do one of the following: double-click at any time to leave it open, or click near its starting point to close it.
How do you plot a curve graph?
2. Select Plot a function from any data table or graph by clicking Analyze, opening the Generate Curve folder, and then selecting the equation, the starting and ending values of X, and the number of curves you want to plot on the first tab (Function).
Is bell curve good or bad?
Employees who have received poor grades may believe that they will be the first to be fired in a difficult job market, resulting in a loss of morale and even worse performance at work.
What is the purpose of a bell curve?
The bell curve distribution is a way of determining how data is distributed when plotted in a graph; if the data is evenly distributed, you will always end up with a bell-shaped curve.
What type of function is a bell curve?
A bell-shaped function, also known as a “bell curve,” is a mathematical function that has a characteristic “bell”-shaped curve, is continuous or smooth, asymptotically approaches zero for large negative/positive x, and has a single, unimodal maximum at small x.