Introduction to Statistical Calculations

DreamCalc Pro supports an extensive range of statistical and regression functions. As a rule, these are screen menu driven using the [S-SUM], [S-VAR] and [DISTR] menu buttons. To input a function, simply press the appropriate button and select the required function from the on-screen menu. Press the menu button repeatedly to scroll through menu screens.

statistical menu
DISTR On-Screen Menu Options

Statistical Modes

You can quickly change the statistical mode by pressing the [STAT] button and selecting from the menu. Currently, the calculator supports the following modes:

Standard Deviation
Linear Regression
Logarithmic Regression
Exponential Regression
Power Regression
Inverse Regression

You can also change modes using the 'Modes' drop-down menu option, or by pressing the [MODE] button. However, the latter is more long-winded.

The calculator stores standard deviation and regression data lists separately. You can, therefore, switch between modes without loss of data. It will also store all statistical data when the application exits, unless you explicitly configure it not to do so from the Options Window.

Standard Deviation (SD) Mode

In Standard Deviation mode, statistical data is maintained in a paired value-frequency form. Therefore, giving a value a frequency of greater than one will have the same effect as entering it multiple times.

Regression Modes

In regression modes, statistical data is stored in the form of x-y paired values. Regression is performed according to the relationships shown below.

Regression Mode	Formula
Linear	y = A + B x
Logarithmic	y = A + B ln(x)
Exponential	y = Ae^{B x}
Power	y = Ax^B
Inverse	y = A + B / x

Entering Statistical Data

There two ways to enter statistical data. By far the most efficient way is to use the Numerical Data List Window, which provides a spreadsheet style interface and is intuitive and easy.

If, however, you are so inclined, you can use the [DATA] and [:] buttons on the main keypad, where [:] is used to separate paired values. For example, if you were in a regression mode and wanted to enter the point x = 115, y = 72, you would key in: {115} [:] {72} [DATA].

In standard deviation mode, [:] separates between the value and it's frequency. If the separator is omitted, a frequency value of one is assumed.

Pressing [SHIFT] [CLD] clears all statistical (and financial cash-flow) data, while pressing [SHIFT] [<-DATA] deletes the last statistical data item from the list.

Examples

Standard Deviation

1. Calculate the Sum, Mean, Std, Sample Std and Std Error for the following data: 23.8, 13.2, 15.9, 32, 28.5, 39 and 24.9.

[S-SUM] -> S:x = 177.3
[S-VAR] -> mean = 25.3285...
[S-VAR] -> std(N) = 8.2807...
[S-VAR] -> std(N-1) = 8.9442...
[S-VAR] -> stderr = 3.1298...

Using this data, calculate the normalized variant t of 32, and the confidence interval for an alpha value of 0.99.

{32} [DISTR] -> t(x) = 0.8056...
{0.99} [DISTR] -> conf(a) = 0.0394...

Note, the latter two examples assume the standard order setting. In text book order mode, key in the following instead:

[DISTR] -> t(x) {32} [=] 0.8056...
[DISTR] -> conf(a) {0.99} [=]0.0394...

Linear Regression

Put the calculator into linear regression mode using the [STAT] button, and enter the following sample data.

Atomic Number (X)	Atomic Weight (Y)
10	20.1797
20	40.078
30	65.39
40	91.224
50	118.71
60	144.24
70	173.04
80	200.59

Calculate the coefficients A and B, for a line of best fit where: y = A + B x.

[SHIFT] [R-A] = -10.7320...
[SHIFT] [R-B] = 2.6091...

Calculate the correlation coefficient, and determine an estimated atomic weight given an atomic number of 55.

[SHIFT] [R-r] = 0.9991...
{55} [SHIFT] [f(x)] = 132.7733

Note, the last example assumes the standard order setting. In text book order mode, key in:

[SHIFT] [f(x)] {55} [=] 132.7733