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Excel has some very useful functions for finding areas under the normal distribution. NORMSDIST (z) Z is the value for which you want the distribution. Returns the standard normal cumulative distribution function. The distribution has a mean of 0 (zero) and a standard deviation of one.
The Excel NORM.DIST function returns values for the normal probability density function (PDF) and the normal cumulative distribution function (CDF). The PDF returns the values of points on the curve. The CDF returns the area under the curve to the left of a value.
Nov 28, 2021 · This video shows how to find areas under the normal curve (in Excel or GoogleSheets using =NORM.S.DIST ()) for the probabiity questions below: a) P (-1.98 ≤ z ≤ 0) 0:49 b) P (z ≤ 1.21 and z...
- 8 min
- 6.9K
- Joshua Emmanuel
In this video, I demonstrate how to find the area under the normal curve using Excel. Technology makes the process quicker than using a table.
- 9 min
- 14.6K
- Math and Stats Help
- Getting Started
- Step #1: Find The mean.
- Step #2: Find The Standard deviation.
- Step #3: Set Up The X-Axis Values For The Curve.
- Step #4: Compute The Normal Distribution Values For Every X-Axis Value.
- Step #5: Create A Scatter Plot with Smooth lines.
- Step #6: Set Up The Label Table.
- Step #7: Insert The Label Data Into The Chart.
- Step #8: Change The Chart Type of The Label Series.
- Step #9: Modify The Horizontal Axis Scale.
For illustration purposes, let’s assume you have the test scores of 200 students and want to grade them “on a curve,” meaning the students’ grades will be based on their relative performance to the rest of the class:
Typically, you are given the mean and SD values from the start, but if that’s not the case, you can easily compute these values in just a few simple steps. Let’s tackle the mean first. Since the mean indicates the average value of a sample or population of data, you can find your standard measurement using the AVERAGEfunction. Type the following fo...
One down, one to go. Fortunately, Excel has a special function to do all the dirty work of finding the standard deviation for you: Again, the formula picks all the values from the specified cell range (B2:B201) and computes its standard deviation—just don’t forget to round up the output as well.
Basically, the chart constitutes a massive number of intervals (think of them as steps) joined together with a line to create a smooth curve. In our case, the x-axis values will be used to illustrate a particular exam score while the y-axis values will tell us the probability of a student getting that score on the exam. Technically, you can include...
Now, find the normal distribution values—the probability of a student getting a certain exam score represented by a particular x-axis value—for each of the intervals. Fortunately for you, Excel has the workhorse to do all these calculations for you: the NORM.DIST function. Type the following formula into the cell to the right (F4) of your first int...
Finally, the time to build the bell curve has come: 1. Select any value in the helper table containing the x- and y-axis values (E4:F153). 2. Go to the Inserttab. 3. Click the “Insert Scatter (X, Y) or Bubble Chart” button. 4. Choose “Scatter with Smooth Lines.”
Technically, you have your bell curve. But it would be hard to read as it lacks any data describing it. Let’s make the normal distribution more informative by adding the labels illustrating all the standard deviation values below and above the mean (you can also use them for showing the z-scores instead). For that, set up yet another helper table a...
Now, add all the data you have prepared. Right-click on the chart plot and choose “Select Data.” In the dialog box that pops up, select “Add.” Highlight the respective cells ranges from the helper table—I2:I8 for “Series X values” and J2:J8 for “Series Y values”—and click “OK.”
Our next step is to change the chart type of the newly-added series to make the data markers appear as dots. To do that, right-click on the chart plot and select “Change Chart Type.” Next, design a combo chart: 1. Navigate to the Combotab. 2. For Series “Series2,” change “Chart Type” to “Scatter.” 2.1. Note: Make sure “Series1” remains as “Scatter ...
Center the chart on the bell curve by adjusting the horizontal axis scale. Right-click on the horizontal axis and pick “Format Axis” from the menu. Once the task pane appears, do the following: 1. Go to the Axis Optionstab. 2. Set the Minimum Bounds value to “15.” 3. Set the Maximum Bounds value to “125.” You can tweak the axis scale range however ...
Sep 28, 2020 · This tutorial explains how to use the z table to answer the following four types of these questions: Find the area under the curve less than some value. Find the area under the curve greater than some value. Find the area under the curve between two values. Find the area under the curve outside of two values.
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Aug 5, 2024 · Make sure your data follows a normal distribution for the best results. Use the ‘TRUE’ argument for cumulative distribution if you want the area under the curve. Consider creating a bell curve chart for a visual representation of your data’s distribution.
