Populations Samples And Processes

What is data?
Data is a collection of facts.

What are engineers and scientists constantly exposed to and where are they exposed to it?
Engineers and scientists are constantly exposed to data in their professional capacities and everyday activities.

What does the discipline of statistics provide?
The discipline of statistics provides methods for organizing and summarizing data, and for drawing conclusions based on the information contained in the data.

What is a population?
A population is a well-defined collection of objects.

What does an investigation typically focus on?
An investigation typically focuses on a population of interest.

Two examples of a population of interest
  1. All gelatin capsules of a particular type produced during a specified period.
  2. All individuals who received a B.S. in engineering during the most recent academic year.

What is it called when desired information is available for all objects in the population?
When desired information is available for all objects in the population, it is called a census.

What factors usually make a census impractical or infeasible?
Factors that usually make a census impractical or infeasible include constraints on:

  • Time.
  • Money.
  • Other scarce resources.

What is a sample?
A sample is a subset of the population chosen in some prescribed manner.

Two examples of a sample
  1. A sample of bearings from a particular production run as a basis for investigating whether bearings are conforming to manufacturing specifications.
  2. A sample of last year's engineering graduates to obtain feedback about the quality of the engineering curricula.

What are you usually only interested in with the objects in a population?
With the objects in a population, you're usually only interested in certain characteristics about them.

Four examples of characteristics you might be interested in with objects in a population
  1. Flaws on the surface of each casing.
  2. Thickness of each capsule wall.
  3. The gender of an engineering graduate.
  4. The age at which the individual graduated.

What are the two types of characteristics?
The two types of characteristics are:

  1. Categorical.
  2. Numerical.

What is the value of a categorical characteristic?
The value of a categorical characteristic is a category.

What is the value of a numerical characteristic?
The value of a numerical characteristic is a number.

What is a variable?
A variable is any characteristic whose value may change from one object to another in the population.

How will you initially denote variables?
You will initially denote variables with the lowercase letters at the end of the alphabet.

Examples of denoting variables with the lowercase letters at the end of the alphabet
  • - Brand of calculator owned by student.
  • - Number of visits to a particular website during a specified period.
  • - Braking distance of an automobile under specified conditions.

What does data result from?
Data results from making observations on at least one variable.

What does a univariate data set consist of?
A univariate data set consists of observations on a single variable.

Example of a categorical univariate data set consisting of the type of transmission for ten vehicles

M A A A M A A M A A

Example of a numerical univariate data set consisting of the pulse rate of patients recently admitted to an adult intensive care unit

88 80 71 103 154 132 67 110 60 105

What does a bivariate data set consist of?
A bivariate data set consists of observations on each of two variables.

Example of a what a bivariate data set could consist of

A height and weight pair for each basketball player on a team.

What does a multivariate data set consist of?
A multivariate data set consists of observations on more than one variable.

Example of what a multivariate data set could consist of

The systolic blood pressure, diastolic blood pressure, and serum cholesterol level for each patient participating in a study.