Section V. Significant Figures

s. 5.5 X 10-3

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9.1 X 106

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t. 10-8

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Section V. SIGNIFICANT FIGURES

1-26. DISCUSSION

The validity of a number depends upon the precision to which the number was

determined.

a. For example, an individual counted the number of ants that were in an anthill

and reported that there were 246,337 ants. This number is obviously inaccurate since

during the period of the count, ants died and others hatched. A more realistic number of

ants would have been 246,000, or 2.46 X 105.

b. A common pitfall is the manner in which laboratory values are reported. The

specialist can use a calculator to determine the value of an unknown specimen and

report a value to the physician that is inaccurate. For example, in using the photometric

equation, the value for glucose in a clinical specimen was determined to be 99.1825734

using the calculator. It would be absurd to report this value since the limits of accuracy

of the measuring device used to obtain the calculation data (accuracy of the test)

allows, at best, only a value of 99.

c. In most cases, the number of significant figures in your least accurate piece of

data used in your calculations determines the accuracy of reported results.

1-27. DETERMINING THE NUMBER OF SIGNIFICANT FIGURES IN A NUMBER

a. Nonzero Integers. All nonzero integers are significant figures.

b. Use of Zero. A zero in a number may or may not be significant, depending

upon the manner in which it is used.

(1) Zeros used to locate decimal points. If one or more zeros are used to

locate a decimal point (place holder) they are not significant. For example, the numbers

0.025, 0.0025, and 0.00025 each have only two significant figures, the two and the five.

(2)

Zeros appearing between numbers. When a zero appears between

MD0837

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