Microsoft Office Tutorials and References

In Depth Information

**Theories About Standard Deviation**

Figure 14.11.

Figure 14.11.
Although the averages are the same, the dispersion measure-

Although the averages are the same, the dispersion measure-

ments paint a different picture of these populations.

ments paint a different picture of these populations.

The fish in the museum tank have an average deviation of 1.45 inches from the

mean. Cells C6, C8, and C10 walk through the calculation of squares of de-

viation, variance, and standard deviation. The theory about standard devi-

ation says that of the fish in the tank, 95% occur between 15.08 inches and

22.07 inches.

The fish at the coral reef have an average deviation of 6.7 inches from the

mean. Cells G6, G7, and G9 walk through the calculation of squares of de-

viation, variance, and standard deviation. The theory about standard devi-

ation says that of the fish at the coral reef, 95% will be between 0.78 inches

and 36.37 inches long.

Comparing these two results helps you to picture the likely populations of

both locations. Although both have the same mean size, the variety of fish

(that is, the measure of dispersion) at the coral reef is much higher than that

at the aquarium.