Sample Standard Deviation

Sample standard deviation is a measure of how dispersed the data values are about the mean sample standard deviation assumes the data is a sampling of a larger, complete set of data, and is calculated using n – 1 as a divisor.

„Press {} for the standard deviation of x–values.

„Press {} for the standard deviation of y–values.

The {σº} and {σ¸} keys in this menu are described in the next section, "Population Standard Deviation."

Example: Sample Standard Deviation.

Using the same process–times as in the above "mean" example, May Kitt now wants to determine the standard deviation time (sx) of the process:

15.5

9.25

10.0

12.5

12.0

8.5

Calculate the standard deviation of the times. (Treat all the data as x–values.)

Keys:Display:Description:

{c{´}



15.5



)

9.25

10 12.5  

12 8.5 

)

{}

U¸σºσ¸

) 

Clears the statistics registers. Enters the first time.

Enters the remaining data; six data points entered. Calculates the standard deviation time.

Population Standard Deviation

Population standard deviation is a measure of how dispersed the data values are about the mean. Population standard deviation assumes the data constitutes the complete set of data, and is calculated using n as a divisor.

„Press {σº} for the population standard deviation of the x–values.

„Press {σ¸} for the population standard deviation of the y–values.

11–6Statistical Operations