What percentage of the data falls outside 1 standard deviation of the mean?
Mean ± 1SD = 68.2%
What does that tell you?
To determine the percentage of data that falls outside 1 standard deviation of the mean, you need to know the shape of the distribution and use the empirical rule, also known as the 68-95-99.7 rule.
The empirical rule states that for a normal distribution:
- Approximately 68% of the data falls within 1 standard deviation of the mean,
- Approximately 95% falls within 2 standard deviations,
- Approximately 99.7% falls within 3 standard deviations.
To calculate the percentage of data outside 1 standard deviation, you can subtract the percentage within from 100%.
So, the percentage of data outside 1 standard deviation of the mean can be approximately estimated as 100% minus 68%, which gives us around 32%.
Note that this rule only applies to approximately normal distributions. If the distribution is skewed or not normal, these percentages may not be accurate.