Page last updated Friday May 12, 2017

# Credits:

I didn't create this calculator; I adapted it (with permission) from the original which is at http://web.mst.edu/~gbert/JAVA/uncertainty.HTML .

Here's an OGG video about how to use the calculator.

# Uncertainty Calculator

This is a device for performing calculations involving quantities with known or estimated uncertainties. This is known as error propagation or uncertainty propagation.
It calculates uncertainties two ways:
• most probable uncertainty, also called standard error (or uncorrelated uncertainty), which is used when errors are independent;
• maximum uncertainty, also called maximum error (or correlated uncertainty), which is used when they are not.
There are a couple of radio buttons to choose which type of uncertainty you want to use.

# Why is there no equals sign?

This calculator operates in what is known as postfix mode. That means you input your values for X and Y first, and then you choose what you want to do with them. This will be explained later in the section under Operation. (In many ways this actually makes it easier to use once you get used to it.)

# What calculations can I do?

The calculations may involve algebraic operations such as:
• Z = X + Y
• Z = X - Y
• Z = X * Y
• Z = X/Y
• Z = XY
or mathematical functions of the type:
• Z = 1/X
• Z = |X|
• Z = ln(X)
• Z = log10(X)
• Z = 10X
• Z = eX
• Z = sqrt(X)
• Z = X2
It also includes trigonometric functions. The trig functions assume angles are in radians. There are also functions to convert between degrees and radians.
If uncertainties (dX, dY) are provided for the input quantities (X,Y), the program will perform the operation or function to calculate the answer (Z) and will also calculate the uncertainty in the answer (dZ). The program will assume the value has no uncertainty if an uncertainty is not provided.
FZ and FdZ refer to formatted versions of Z and dZ. These are still being developed (ie. they may not be quite right at present.)

## Mode

Maximum Error Standard Error

±
±

±
±
±

# Operation:

Position the cursor on the blank under "X", click the mouse, and type a value. Alternately, press the TAB key until the cursor appears in this blank, then type the number. In case of an error, use normal text-editing procedures.Enter values for X and dX, and possibly for Y and dY. (The TAB key moves the cursor through the blanks in the order: X, dX, Y, dY).
Click on the button for the desired operation or function. The equation for the calculation appears in the central blank, and the values of Z and dZ appear in their respective blanks.
There are buttons for transferring values from Z to a MEMory location, or to the blanks for X or Y; or from the MEMory to X or Y.

Wilfrid Laurier University