16 PART 1 Getting Started with Biostatistics

We start the chapter by showing you how to interpret the mathematical formulas

you encounter throughout this book. We don’t deconstruct the intricacies of com-

plicated mathematical operations. Instead, we explain how mathematical opera-

tions are indicated in this book. If you feel unsure of your grasp on algebra,

consider reviewing Algebra I For Dummies and Algebra II For Dummies, which are

both written by Mary Jane Sterling and published by Wiley.

Breaking Down the Basics of

Mathematical Formulas

One way to think of a mathematical formula is as a shorthand way to describe how

to do a certain calculation. Formulas are made up of numbers, constants, and

variables interspersed with symbols that indicate mathematical operations, punc-

tuation, and typographic effects. Formulas are constructed using relatively stan-

dardized rules that have evolved over centuries. In the following sections, we

describe two different kinds of formulas that you encounter in this book: typeset

and plain text. We also describe two of the building blocks from which formulas

are created: constants and variables.

Displaying formulas in different ways

Formulas can be expressed in print in two different formats: typeset format and

plain text format:»

» ^{A typeset format utilizes special symbols, and when printed, the formula is}

spread out in a two-dimensional structure, like this:

SD

x

m

n

i

i

n

2

1

1»

» ^{A plain text format prints the formula out as a single line, which is easier to}

type if you’re limited to the characters on a keyboard:

SD

x i

m

i

n

n

sqrt sum

[ ]

^ , , ,

/

2

1

1

You must know how to read both types of formula displays — typeset and plain

text. The examples in this chapter show both styles. But you may never have to

construct a professional-looking typeset formula (unless you’re writing a book,

like we’re doing right now). On the other hand, you’ll almost certainly have to

write out plain text formulas as part of organizing, preparing, editing, and ana-

lyzing your data.