How to Use the Empirical Rule: 7 Steps

The Empirical Rule, also known as the 68-95-99.7 Rule, is a statistical concept that can help you understand the distribution of data in a normal (bell-shaped) curve. This rule states that in a normal distribution:
1. Approximately 68% of the data falls within one standard deviation of the mean.
2. Around 95% of the data lies within two standard deviations of the mean.
3. Nearly 99.7% of values are found within three standard deviations from the mean.
Here is a step-by-step guide on how to use the Empirical Rule:
1. Identify if your data follows a normal distribution: Before applying the Empirical Rule, ensure that your dataset is continuous, symmetric, and follows a bell-shaped curve.
2. Calculate the mean: Find the average value of all data points in your dataset by summing them up and dividing by the number of values. The resulting value represents the center of your bell curve.
3. Calculate the standard deviation: Determine how much each data point deviates from the mean value on average. You can use statistical software or calculators for this purpose.
4. Identify deviations from the mean: Find one, two, and three standard deviations above and below the mean value.
5. Apply the Empirical Rule percentages: Remember that approximately 68% of data falls within one standard deviation, about 95% within two standard deviations, and around 99.7% within three standard deviations from the mean.
6. Compare actual and expected percentages: Use your dataset to count the number of values within each interval (one, two, and three standard deviations from the mean) and divide by the total number of values to obtain actual percentages.
7. Assess accuracy: Compare these actual percentages with those indicated by the Empirical Rule (68%, 95%, and 99.7%). If they match closely, the Empirical Rule was an appropriate tool for analyzing your dataset.
The Empirical Rule is a useful tool for understanding the distribution of your data when it follows a normal distribution. Knowing how to apply this rule not only helps you visualize your data but also allows you to identify anomalies and interpret significance more effectively.