BIOSTATISTICS AND EPIDEMIOLOGY

Introduction to Biostatistics

Statistics

__ is a field of study concerned with (1) the collection, organization, summarization, and analysis of data; and (2) the drawing of inferences about a body of data when only a part of the data is observed.

Biostatistics

When the data analyzed are derived from the biological sciences and medicine, we use the term __ to distinguish this particular application of statistical tools and concepts.

Epidemiology

The study of disease and its treatment, control, and prevention in a population of individuals.

* Data
* Experiments
* Routinely kept records
* Surveys
* External Sources

Sources of Data

Data

__ consists of information coming from observations, counts, measurements, or responses.

Experiments

Frequently the data needed to answer a question are available only as the result of an __. A nurse may wish to know which of several strategies is best for maximizing patient compliance. The nurse might conduct an experiment in which the different strategies of motivating compliance are tried with different patients. Subsequent evaluation of the responses to the different strategies might enable the nurse to decide which is most effective.

Routinely kept records

It is difficult to imagine any type of organization that does not keep records of dayto-day transactions of its activities. Hospital medical records, for example, contain immense amounts of information on patients, while hospital accounting records contain a wealth of data on the facility’s business activities. When the need for data arises, we should look for them first among __.

Surveys

If the data needed to answer a question are not available from routinely kept records, the logical source may be a __.

External sources

The data needed to answer a question may already exist in the form of published reports, commercially available data banks, or the research literature. In other words, we may find that someone else has already asked the same question, and the answer obtained may be applicable to our present situation.

Population

__ is the collection of all outcomes, responses, measurement, or counts that are of interest.

Sample

__ is a subset of a population.

Parameter

__ is a numerical description of a population characteristic.

Statistic

__ is a numerical description of a sample characteristic.

* Descriptive
* Inferential Statistics

Two branches of Statistics

Descriptive Statistics

Involves the organization, summarization, and display of data.

Inferential statistics

Involves using a sample to draw conclusions about a population.

Variable

If, as we observe a characteristic, we find that it takes on different values in different persons, places, or things, we label the characteristic a __.

Quantitative Variables

We can obtain measurements on the heights of adult males, the weights of preschool children, and the ages of patients seen in a dental clinic. These are examples of __.

Qualitative Variables

When an ill person is given a medical diagnosis, a person is designated as belonging to an ethnic group, or a person, place, or object is said to possess or not to possess some characteristic of interest. We refer to variables of this kind as __. Measurements made on __ convey information regarding attribute.

Random Variable

When the values obtained arise as a result of chance factors, so that they cannot be exactly predicted in advance, the variable is called a __.

Discrete Random Variable

A __ is characterized by gaps or interruptions in the values that it can assume. These gaps or interruptions indicate the absence of values between particular values that the variable can assume.

Continuous Random Variable

A __ does not possess the gaps or interruptions characteristic of a discrete random variable. A continuous random variable can assume any value within a specified relevant interval of values assumed by the variable.

* Nominal
* ordinal
* interval
* ratio

Levels of Measurement from lowest to highest:

Nominal

Calculated using names, labels, or qualities. No mathematical computations can be made at this level. Data at the __ level of measurement are qualitative only.

Ordinal

Arranged in order, but differences between data entries are not meaningful. Data at the __ level of measurement are qualitative or quantitative.

Interval

Arranged in order, the differences between data entries can be calculated. Data at the __ level of measurement are quantitative. A zero entry simply represents a position on a scale; the entry is not an inherent zero.

Ratio

A __ of two data values can be formed so one data value can be expressed as a *. Data at the* _ level of measurement are similar to the interval level, but a zero entry is meaningful.

* Simple random sample
* systematic sample
* stratified sample
* cluster sample

List of sampling techniques:

Simple random sample

If a sample of size n is drawn from a population of size N in such a way that every possible sample of size n has the same chance of being selected, the sample is called a __.

Systematic sample

__ is a sample in which each member of the population is assigned a number. A starting number is randomly selected and sample members are selected at regular intervals.

Stratified

A __ sample has members from each segment of a population. This ensures that each segment from the population is represented.

Cluster

A __ sample has all members from randomly selected segments of a population. This is used when the population falls into naturally occurring subgroups.