Deviation standard 14. 0, 14.0, 14.1, 14.2, 14.4, 14.5, 14.5, 14.5, 14.6, 14.6, 14.6, 14.7, 14.7, 14.8, 14.8, 14.8, 14.8, 14.9, 14.9, 14.9, 15.0, 15.0, 15.1, 15.2, 15.3, 15.5, 15.8, 15.8, 16.0, 16.1

The standard deviation is a measure of how "tight" the samples are distributed around your mean.
In layman's terms, a small standard deviation indicates that most of your measurements are in the vicinity of the means; a large standard deviation corresponds to readings that are all over the place.
You could also say that the smaller the SD, the more your mean is representative of the data set.
For a better explanation, just look up Standard deviation on Wikipedia!

If you mean the standard deviation, there are two shifted keys on the third row marked with a lower-case Greek sigma. sigma_xn is the population standard deviation and sigma_xn-1 is the sample standard deviation.

Yes. The sample standard deviation is 2nd [sigma x n-1] and the population standard deviation is 2nd [sigma x n].

Jill. She scored two standard deviations above the mean, while he only scored one-and-a-half standard deviations above the mean.

Press 2ND [CSR] to clear the stat data.

For each data point, enter the number followed by SIGMA+

If you have grouped data, enter the number followed by 2ND [FRQ] followed by the frequency then SIGMA+

Press 2ND [sigma x n] for the population standard deviation or 2ND [sigma x n-1] for the sample standard deviation.

I want to calculate a standard deviation on BA II plus

Standard deviation is the average root mean squared deviation from the average of the numbers.

Familiarize yourself with the wikipedia page on standard deviation: http://en.wikipedia.org/wiki/Standard_deviation

In this case, your question is easy. The standard deviation is 0, so this means the boys ages are all the same.

So they're all 24/3 = 8 years old.

Proof:
8 + 8 + 8 = 24 <-- satisfies the constraint that the boys ages must total to 24.

Get the standard deviation of these numbers;

8+8+8 / 3 = 8 <-- the average value is 8

The deviation of each boy's age from the average is:
boy 1
--------
8 years old, which deviates from 8 by 0
boy 2
--------
8 years old, which deviates from 8 by 0
boy 3
--------
8 years old, which deviates from 8 by 0

So the deviations are 0, 0 and 0.

To get the standard deviation, you sum the squares of the deviations of each boy, get the average, and square root. So:

0² + 0² + 0² = 0
Average is 0 / 3 = 0
Square root of 0 = 0

So the standard deviation is 0. Which shouldn't be much of a surprise to you. We just had to actually DO the work to show that it was in fact 0.

Texas Instruments TI-86 Statistics How-To Information The following instructions should allow you to calculate the mean and standard deviation using a TI-86 calculator.

1. Press STAT
2. Select EDIT
3. Enter data into a list: [2.32 ENTER 2.43 ENTER 2.39 ENTER, etc.] Continue until all data have been entered. (use arrows keys to go to the y value, if any)
   
4. EXIT until you reach the main ("blank") screen. (If you try to calculate while you're in the data menu, it thinks you're still trying to enter data!)
5. Press STAT
6. Select CALC
7. Select OneVa
8. Select LIST, NAMES, xStat(F2), Press ENTER
9. The calculator provides Max, Min, Mean, Standard Deviation, Sum, Sigma, etc. You will be primarily interested in the Mean and Standard Deviation (sx).

StdDev( {1,2,3,4,5,6,7,8,9,10} )
with your list inside the curly braces.

This calc will do standard deviations. In the manual it is on page 2 and also on page 40.