# How does the concept of significant figures relate to uncertainty in measurement

According to sources, in any measurement, the number of significant figures is critical. The number of significant figures is the number of digits believed to be correct by the person doing the measuring. It includes one estimated digit. The concept of significant figures only deals with precision and not with accuracy.

For example, consider measuring the length of a metal rod several times with a ruler. You will get essentially the same measurement over and over again with a small reading error equal to about 1/10 of the smallest division on the ruler. You have determined the length with high precision.

However, you don't know if the ruler was accurate to begin with; you don't know the accuracy of your measuring device unless you calibrate it.

Rules for Working with Significant Figures:

1. Leading zeros are never significant; imbedded zeros are always significant; trailing zeros are significant only if the decimal point is specified. Hint: Change the number to scientific notation. It is easier to see.

2. Addition or Subtraction: The last digit retained is set by the first doubtful digit.

3. Multiplication or Division: The answer contains no more significant figures than the least accurately known number.

Find significant figures tips and tutorials at the University of South Carolina.

Speaking of measurement, this country’s waistline is growing bigger by the year and poses a greater threat to a person’s health than being overweight or even obese.

A research team from the Centers for Disease Control and Prevention (CDC) examined measurements from Americans’ stomachs from 1999 to 2012 and found the average waist circumference “increased progressively and significantly,” highlighting the increasing threat of stomach fat. Read more at Medical Daily.

Updated on Wednesday, September 24 2014 at 10:17AM EDT
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