How do I work out the standard deviation, every time I try to work it out it keeps saying error 2.

Mean absolute deviation.
Let's break it down into its components.
Mean - Average
Absolute - absolute value - sign doesn't matter - if negative, make positive
Deviation - difference from the mean

Let's do an example. Population 3 7 4 2. Total 16. Mean (Average) 16/4 = 4.

Deviations
3 - 4 = -1 absolute value 1
7 - 4 = 3
4 - 4 = 0
2 - 4 = -2 absolute value 2

Sum of these deviations 1 + 3 + 0 + 2 = 6
Mean (average) of these deviations is 6 / 4 = 1.5.

Good luck,

Paul

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!

This is to be expected. A standard deviation of 0 means that all the data points are identical. Asking for the point below which .025 of the data lie is meaningless.

The normalcdf function takes three arguments: the z value, the mean, and the standard deviation. In the "standard" case the mean is 0 and the standard deviation is 1. Thus, try calculating
normalcdf(-.1923, 0, 1) .

Hello,
I am happy that you found my solution helpful and even flattered that you copied it in this thread. By doing this, you gave me the opportunity to discover an error in my post. In fact, the calculator does provide a column for the frequency. If you enter nothing in the frequency column, all data items will have their frequency set to 1, by default.

Back to the current subject: How to get the variance (the square of the standard deviation).
When you finish entering your data:

1. Press the [AC] button to exit the data editor.
2. Press [****][STAT].
   
3. Press [5:Var] to open the statistical result selection screen.
4. Press [3: xSigma_n] or [4:xSigma_n -1] depending on what you are interested in (population or sample) standard deviation.
5. The screen echoes the symbol for the value selected (the value displayed on the bottom line may be 0 or an old value from a previous calculation: it is not the value you have just calculated).
   
6. Press [=] to display the current value of the SD chosen.
7. By doing this you are in fact storing it it answer memory.
8. All you have to do now is to raise it to power 2 by pressing the [x^2] key ( the one above the [HYP] key).
9. The calculator will display Ans^2.
10. Press [=] to display the value of the variance.

If you are not interested in the value of the standard deviation, but just want the variance, follow the foregoing procedure until step #5.
While the symbol xSigma_n or xSigma_n-1 is still displayed with the blinking cursor to its right, press the [x^2] key above the [HYP] key. The screen displays say xSigma_n ^2. Press [=] to calculate the variance.

As my motto says, I am always happy to help, but happier still when people show true appreciation.

Hope it helps.

Hello,
I am afraid I do not understand. The frequency of a PARTICULAR score is the number of times that particular value occurs in the data. It is not the number of data.
Ex: the data are:
4, 6, 5, 4, 4, 8, 9, 3, 3, 6, 7
Frequency of (3) =2
Frequency of (4)= 3
Frequency of (5) =1
Frequency of (6)= 2
Frequency of (7)=1
Frequency of (8)=1
Frequency of (9)=1

Number of data =11 (n=11)

You compute the mean M
M= (2x3 + 3x4 +1x5 +2x6+1x7+1x8+1x9) /11 =5.363636..
As you can see, if a term is not repeated it is multiplied by 1 (its frequency is one). Value 3 occurs twice (hence 2x3); value 4 occurs 3 times (3x4), etc.

To calculate by hand the sum of squares
3: (3-5.3636)^2 + (3-5.3636)^2 .................... = 2x(3-5.3636)^2
4: (4-5.3636)^2 + (4-5.3636)^2 +(4-5.3636)^2 = 3x(4-5.3636)^2
5: (5-5.3636)^2 ...................................... .= 1x(5-5.3636)^2
6: (6-5.3636)^2 +(6-5.3636)^2......................= 2x(6-5.3636)^2
7: (7-5.3636)^2.......................................... .=1x(7-5.3636)^2
8: (8-5.3636)^2......................................... ..=1x(8-5.3636)^2
9: (9-5.3636)^2......................................... ..=1x(9-5.3636)^2
If I have not made a mistake the sum of squares is 40.5454

Standard Deviation

The standard formula above gives s= square root (40.5454/10) =2.01
Population Standard Deviation

The population Standard deviation above is S= square root (40.5454/11) =1.9198

So if you perform the calculation with the calculator the only times you need to enter the frequency is for repeated terms. When you have to enter 6 above, its frequency is 2 you proceed as follows
6 [2nd][FRQ] 2 [Sigma+]

Once you entered the raw scores, the calculator does the rest.
Hope it helps.

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.

Enter 1 then press the (SIGMA)+ button (SIGMA) looks like a sideways capital M ....its a Greek letter.

Then enter 2 and press the (SIGMA)+ button
Then enter the next value and press the (SIGMA)+ button

After you press the (SIGMA)+ button the calculator displays the number of numbers you have entered

Once all numbers of your sample have been entered press 2nd and the button corresponding to x-bar

sample st. dev is the (sigma)n-1 button (need to use 2nd button)
variance is (std. dev.)^2

population st. dev is the (sigma)n-1 button (need to use 2nd button)
variance is (std. dev.)^2

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