# Considering your data

When we gather lots of data bout some geologic process, we need to have a
look at the data and consider its basic properties. To do this, we can use
Statistics. This lecture will not do much justice to the study of
statitsitcs or its application to geologic problems, but it should point
you to an essential task when you consider your data.

You have to be careful however, that the description of your data
(statistics) does not get in the way of your thinking.

I found this book to be useful:

Waltham, D., 1994, Mathematics: a simple tool for geologists, New York: Chapman and
Hall, 189 p.

## Measures of location

These are representative of the data:

Mean = (1/n)*sum of all values

Mode = value which occurs with the greatest frequency

Median = the middle value of a set of numbers arranged in order

## Measures of dispersion

Range = xmax - xmin

Standard deviation is a measure of dispersion in the sample data:
S^{2} = (1/(n-1))*Sum (x - xbar)^{2}

xbar is the mean of the dataset.

+/- 3 standard deviations always contains >90% of the data. Units are the
same as the data. Used to standardize the data set.

## Regression and plotting using Kaleidagraph

See assignment 6 for a summary of how Kaleidagraph may be used for
regression.

Pages maintained by

Prof. Ramón Arrowsmith
Pages last modified on Thurs Oct 10 1997.