## On Being Stoned

### Charles T. Tart, Ph. D.

#### A Note to the Non-Scientist Reader

In order to conveniently present exact findings to the researchers
who read this book, there are lots of parentheses filled with
numbers and simple statistics.

If you aren't interested in the *exact* findings, or if numbers
and statistics turn you off, there's a simple way to avoid any
problem: ignore them. Everything has been written in plain English,
and the numbers confined to parentheses for just this reason!

If, on the other hand, you haven't a formal background in statistics
but would like to know what the probability figures in the parentheses
(such as "p < .05") mean, it all boils down to this:
how do you know when a difference in the way two groups of people
answer a question is a meaningful, *significant* difference,
and how do you know when it results only from the random variation
you get whenever you deal with people's responses?

You never know for *certain* which is which, but a statistical
test is an objective way of being reasonably sure, one way or
the other. Statistical tests use the known mathematical properties
of numbers to let you decide when a difference is probably due
to chance, and when a difference is so large that chance seems
unlikely. The exact mathematics aren't of interest to the general
reader, but only the outcome, the probability figure. If the outcome
of a particular test could have happened by chance only five or
fewer times in a hundred trials (conventionally expressed in this
book as p<.05, probability equal to or less than 5/100),* we
begin to doubt that this is chance variation. It probably represents
a real difference between the groups. If the probability is even
smaller that the outcome is due to chance, say less than one in
a hundred (p < .01) or less than one in a thousand (p <
.001), we can feel quite certain that we are dealing with real,
important differences.**

Thus in this book the lower the probability figure in parentheses,
the greater the difference between the groups being compared.

#### Footnotes

*More exactly, the sign should be [less than *or equal to*]
rather than simply <, but this simplification will be used
throughout the text.

**Statistical tables available to me only go up to the .0005 level.
When I use the notation p << .0005, the difference is even
more significant; when I use p <<< .0005, it is *super*significant.
For the technically minded, I use p << .0005 when chi square
is greater than or equal to 50, and p <<< .0005 when
chi square is greater than or equal to 100, with four degrees
of freedom in each case.

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