biostatist

BiostatisticsIntroduction

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Article for Review

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It is difficult to look at DATA in raw form

Variable: is a characteristics or a property that may take on different values.
Height
Weight
Sex
Disease
Occupation
Religion

Statistics

Two Meanings
Specific numbers
Method of analysis

Specific number

numerical measurement determined by a set of data
Example: Twenty-three percent of people

Statistics

Method of analysis
a collection of methods for planning experiments, obtaining data, and then organizing, summarizing, presenting, analyzing, interpreting, and drawing conclusions based on the data

Statistics

Definitions
Population
the complete collection of all elements (scores, people, measurements, and so on) to be studied. The collection is complete in the sense that it includes all subjects to be studied.

Definitions

Census
the collection of data from every element in a population
Sample
a subcollection of elements drawn from a population

The Nature of Data

Parameter
a numerical measurement describing some characteristic of a population

Definitions

Parameter
a numerical measurement describing some characteristic of a population

population

parameter

Definitions

Definitions

Statistic

a numerical measurement describing some characteristic of a sample

Definitions

Quantitative data
numbers representing counts or measurements
Qualitative (or categorical or attribute) data
can be separated into different categories that are distinguished by some nonnumeric characteristics

Definitions

Quantitative data
the incomes of college graduates

Definitions

Quantitative data
the incomes of college graduates
Qualitative (or categorical or attribute) data
the genders (male/female) of college graduates

Discrete

data result when the number of possible values is either a finite number or a ‘countable’ number of possible values
0, 1, 2, 3, . . .

Definitions

Discrete
data result when the number of possible values is either a finite number or a ‘countable’ number of possible values
0, 1, 2, 3, . . .
Continuous
(numerical) data result from infinitely many possible values that correspond to some continuous scale that covers a range of values without gaps, interruptions, or jumps

Definitions

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Discrete

The number of eggs that hens lay; for example, 3 eggs a day.

Definitions

Discrete
The number of eggs that hens lay; for example, 3 eggs a day.
Continuous
The amounts of milk that cows produce; for example, 2.343115 gallons a day.

Definitions

nominal level of measurement
characterized by data that consist of names, labels, or categories only. The data cannot be arranged in an ordering scheme (such as low to high)
Example: survey responses yes, no, undecided

Definitions

ordinal level of measurement
involves data that may be arranged in some order, but differences between data values either cannot be determined or are meaningless
Example: Course grades A, B, C, D, or F

Definitions

interval level of measurement
like the ordinal level, with the additional property that the difference between any two data values is meaningful. However, there is no natural zero starting point (where none of the quantity is present)
Example: Years 1000, 2000, 1776, and 1492

Definitions

ratio level of measurement
the interval level modified to include the natural zero starting point (where zero indicates that none of the quantity is present). For values at this level, differences and ratios are meaningful.
Example: Prices of college textbooks

Definitions

Levels of Measurement
Nominal - categories only
Ordinal - categories with some order
Interval - differences but no natural starting point
Ratio - differences and a natural starting point