What is the percent error?

Question

Estimated population is 786 and the actual population is 639. 

Answer 1

"Error" is the amount off the number is from the true value. So "Percent Error" is the associated percentage or the amount off the number is from the true value divided by the true value (and then turned into a percent).

In this case, the error is 786 - 639 or 147 so the percent error is 147/639 = 0.23 but that is not a percent, it's a decimal. To turn it into a percent you can either move the decimal point two places or multiply by 100, both are the same thing. So 23% error.