Java Scientific Calculator

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Statistical functions

You can change to statistics mode using the mode button (key ‘?’) followed by ‘2’. This mode lets you find the mean and standard deviation of a single set of data. Each data value can be any complex number.

Data entry

The usual way to enter data is with the Σ+ button (key ‘M’). This button evaluates the current expression, stores the result and returns a number showing the total number of data values now stored. So, for example to store the data 5, 6, 7 do the following. 5 Σ+ (result 1); 6 Σ+ (result 2); 7 Σ+ (result 3). The statistical memory will now contain the three numbers 5, 6 and 7.

If you ever want to remove a data value, you can use the Σ− button (keys shift ‘M’). This has the effect of evaluating the current expression, removing the value from statistical memory and decreaseing the number of data values stored.

Emptying the statistical memory

Use the Scl button (keys shift ‘\’) to clear the statistical memory of data. It is a good idea to do this before entering a new set of data, just in case you left in some old values.

Mean and standard deviation

The calculator provides one mean and two standard deviation functions, one for population standard deviation, one for sample standard deviation.

The mean button (x with a bar over, keys shift ‘m’) puts the arithmetic mean of the current set of data into the current expression. To find its value, evaluate the expression, for example, by using the equals button.

The σn−1 button, (keys shift ‘s’) finds the sample standard deviation (often written sx. This is an unbiased estimator for the population standard deviation and is the usual standard deviation estimator for small samples (less than about 30 data items). So it is usually the standard deviation function you want from a calculator. If you have a bigger sample, a spreadsheet or statistical package may be more appropriate.

The σn button, (keys shift ‘S’) finds the population standard deviation (often written sx. This is a maximum likelihood estimator for the population standard deviation. It is biased and so is not typically used for small samples. It is provided for consistency.

What about other statistical functions?

The calculator limits yout to the three statistical functions found on most calculators and deliberately emulates how these work. It may some day allow you to see the data or provide some other functions. However, regression and correlation functions are unlikely. For anything more than a small data sample, a calculator is not a good way to do statistics. A statistical package like R is better.


Last modified: Sat 31 May 2008 01:11 pm

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