# >> College & Higher Education >> College

How to Find Percents on a Normal Curve

The normal curve, also known as the Gaussian curve or bell curve, shows the distribution of a population (e.g. people, traits such as salary, and temperature). Supposing that you know the mean and standard deviation of the population, you can know the exact shape of a normal curve. However, to use the normal curve in an applied sense (e.g. finding the percentage of a population that is under, above or within certain values), you need to know how to find the percentages associated with points on the normal curve. You can do so using a standard normal table and conversion tricks.

Standard normal table (can be found in almost any introductory statistics text)

Instructions

- 1
  Decide on the range for which you wish to determine the percentage. Recall that the normal curve has an infinite domain (that is, it goes from negative infinity to infinity). Write the domain you wish to find as (a < x < b), where "a" and "b" are the lower and upper limits, respectively.
- 2
  Convert the lower limit. Subtract the mean from "a." Divide the result by the standard deviation. Call this result "L."
- 3
  Find the standard normal curve's percentage corresponding to the converted lower limit. Use the standard normal table to look up the percentage corresponding to "L." Call this percentage "y."
- 4
  Convert the upper limit. Subtract the mean from "b." Divide the result by the standard deviation. Call this result "U."
- 5
  Find the standard normal curve's percentage corresponding to the converted lower limit. Use the standard normal table to look up the percentage corresponding to "U." Call this percentage "z."
- 6
  Calculate the final percentage for the normal curve. Subtract "L" from "U" for the result.

What Type of Technology Do We Use to Study Atoms?

How to Calculate Saturation Mixing Ratio