Page 24 - Statistics and Data Analysis in Geology

Chapter 2

Geologists’ direct observations of our world are confined to the outer part
of the Earth’s crust, yet they must attempt to understand the nature of the Earth’s
core and mantle and the deeper parts of the crust. Furthermore, the processes that
modify the Earth, such as mountain building and continental evolution, are gener-
ally beyond the geologists’ capabilities for direct manipulation. No other scientists,
with the exception of astronomers, are more removed from the bulk of their study
material and less able to experiment on their subject.
Geology, to a major extent, remains a science that is principally concerned with
observation. Because geologists depend heavily on observations, particularly ob-
servations in which there is a large portion of uncertainty, statistics should play
an important role in their research. Although the term “statistics” once referred
simply to the collection of numerical facts such as baseball scores, it has come to
include the analysis of data, and especially the uncertainty associated with such
data. Statistical problems, whether perceived or not, occur wherever there are ele-
ments of chance. Geologists need to be conscious of these problems, and of some
of the statistical tools that are available to help solve the problems.

Pro ba bi I ity

Although many descriptions and definitions of statistics have been written, it per-
haps may be best considered as the determination of the probable from the pos-
sible. In any circumstance, there are a variety (sometimes an infinity) of possible
outcomes. All these have an associated probability that describes their frequency
of occurrence. From an analysis of probabilities associated with events, future be-
havior or past states of the object or event under study may be estimated.
All of us have an intuitive concept of probability. For example, if asked to guess
whether it will rain tomorrow, most of us would reply with some confidence that
rain is likely or unlikely, or perhaps in rare circumstances, that it is certain to rain,
or certain not to rain. An alternative way of expressing our estimate would be to