**Analyze
g Statistics (F6)**

The statistics command brings up a window with several statistical values of all selected data sets. If you draw a selection rectangle before selecting this command, only the data points that fall within the rectangle will be counted*.

The contents of the window are also placed on the clipboard, for easy pasting into other programs.

The meaning of some of the statistical parameters:

**Mean:** the average, or arithmetic mean, which means the
sum of all Y values divided by the number of data points.

**Median (or Q2, or middle value): **the value below which
50% of the data points fall.

Q1:** **the value below which 25% of the data points fall.

**Q3:** ** **the value below which 75% of the data points fall.

**Mode:** the value which occurs the most. A maximum of 20
modes is calculated, if several different values occur an equal number of times.
If all values occur only once, there *is* no mode, in which case "no
mode present" is displayed.

The program calculates the modes with values that are absolutely equal. If you
want to include values that are *approximately* equal, it is better to
calculate a histogram of Y values,
where you can specify bands of Y values.

If statistics is calulated for more data
sets at once, only the first mode of each data set will be shown (if multiple
modes are present within one data set).

**Interquartile mean:** the mean of all data points that
fall between Q1 and Q3. Can be useful to ignore extreme values (spikes for
example).

**Mean of absolutes:** the average of the absolute values
of all Y values.

**RMS:** Root Mean Square value. To calculate RMS: square
all the values, take the average of the squares and then take the square root of
the average. Is used mostly for trigonometric functions (sinuses etcetera). For
example, your AC mains voltage is indicated in RMS.

**Harmonic mean:** 1 / (the sum of the reciprocals of all
Y values, divided by the number of data points).

**Geometric mean: **The n-th root of the product of all Y
values, where n is the number of data points. Used for example to calculate an
average annual return of interest.

**Variance: **,
where N is the number of data points. When calculating the variance of a
sample, N-1 is used instead of N.**
Standard deviation: **the square root of the variance. It is the most common
way to measure spread.

**Semi-interquartile range**: Another way to measure
spread: (Q3-Q1)/2. Since half the values in a distribution lie between Q3 and
Q1, the semi-interquartile range is 1/2 the distance needed to cover 1/2 the
number of data points.

Some good web sites on statistics can be found here, here and here.