Statistics Chapter One

Statistical Basics and Data Collection

Statistics

The study of how to collect, organize, analyze and be able to interrupt material information from data.

Individuals

The people or objects to be included in the type of the study.

Variables

The characteristics of those individuals that are to be measured or observed.

Categorical variable

Places an individual into certain categories or groups. Also called qualitative. Examples include major, housing, and hometown.

Quantitative variable

Has value or numerical measurement for which arithmetic operations such as addition or averaging make sense. (Think of it as the quantity of something) Ex. GPA

Population

The data from every individual of interest. A parameter is a numerical measure that describes the aspect of a population. Ex. The average study time per week for all of the students at school.

Sample

The data from one some of the individuals of interest. A statistic is a numerical measure that describes an aspect of a sample. Ex. 100 randomly selected students from school. The statistic would be the average study time then of those 100 students.

Bias

In some cases, when it systematically favors certain type of outcomes.

SRS (simple random sample)

A size of # of individuals from the population that is chosen in such a way that every set # of individuals has an equal chance to be the sample that is actually selected.

Sampling error

Occurs when a sample is being used instead of the entire population.

Non-sampling error

Occurs because of mistakes or problems in how data are collected, measured, or recorded. These errors can occur even when a census is used.

Undercoverage

Occurs when some groups in the population have no chance of being included in the sample.

Response error

Occurs when a subject gives an incorrect response. Mostly occurs in surveys.

Non-response error

Is the failure to obtain data from an individual selected for a sample because the subject cannot be contacted or those who are contacted refuse to cooperate.

Observational study

The observations and measurements of individuals are conducted in a study that doesn’t change the response or the variable being measured.

Sample surveys

Are an important kind of observational study. They end up choosing a sample from a specific population and use the sample to get information then from the entire population.

Census

Attempts to measure every individual in the population.

Experiment

A treatment is deliberately imposed on the individuals in order to observe a possible change in the response or variable being measured.