Data Collection, Sampling Techniques, and Frequency Distributions

Vocabulary flashcards covering sampling techniques, observational vs. experimental studies, misuses of statistics, and frequency distribution graphing techniques.

Probability Sampling

A sample selection process in which all members of the population have an equal chance of being selected.

Simple Random Sampling

A probability sampling technique where the researcher sets criteria for choosing the sample from the population so that targeted demographics are included.

Systematic Random Sampling

A probability sampling technique where the first individual is chosen in random form, while subsequent subjects are selected in a systematic manner.

Stratified Random Sampling

A probability sampling technique that allows the selection of each individual from a particular group of the targeted sample.

Cluster Random Sampling

A probability sampling technique where the researcher chooses random clusters from the population whose members share similarities with one another.

Non-Probability Sampling

A sampling process in which not all members of the population have a chance of being selected.

Convenience Sampling

A non-probability sampling technique where participants are selected based on whoever is easiest to reach.

Quota Sampling

A non-probability sampling technique used to fill predetermined quotas for specific subgroups, such as $50$ men and $50$ women.

Judgement Sampling

A non-probability sampling technique in which the researcher selects sample members based on their own expertise.

Snowball Sampling

A non-probability sampling technique in which existing study participants recruit other participants.

Observational Study

A statistical study in which the researcher merely observes what is happening or has happened in the past and draws conclusions without research intervention.

Cross-sectional Study

An observational study in which all the data are collected at one time.

Retrospective Study

An observational study in which data are collected using records obtained from the past.

Longitudinal Study

An observational study in which data are collected over a period of time covering both past and present.

Experimental Study

A statistical study in which the researcher manipulates one of the variables and tries to determine how the manipulation influences other variables.

Independent Variable

Also called the explanatory variable, it is the variable in an experimental study that is being manipulated by the researcher.

Dependent Variable

Also called the outcome variable, it is the resultant variable measured in an experimental study.

Treatment Group

The group in a study that receives a specific treatment or instruction.

Control Group

The group in a study that does not receive the specific treatment.

Hawthorne Effect

A phenomenon discovered in $1924$ at the Hawthorne plant of the Western Electric Company, where subjects who knew they were participating in an experiment changed their behavior in ways that affected the results.

Placebo Effect

A phenomenon in which subjects respond favorably or show improvement simply due to the fact that they have been selected for the study.

Confounding Variable

Also called a lurking variable, it is a variable that influences the dependent or outcome variable but was not separated from the independent variable.

Detached Statistics

A statistical misrepresentation in which a claim uses a statistic without making any comparison.

Raw Data

Data that are in their original, unorganized form.

Frequency Distribution

The organization of raw data in table form using classes and frequencies.

Class

A quantitative or qualitative category into which each raw data value is placed.

Frequency

The number of raw data values contained in a specific class.

Lower Class Limit

The smallest data value that can be included in a specific class.

Upper Class Limit

The largest data value that can be included in a specific class.

Class Boundaries

Numbers used to separate classes in a frequency distribution so that there are no gaps between them.

Class Width

The numerical distance found by subtracting the lower boundary from the upper boundary for any given class.

Grouped Frequency Distribution

A frequency distribution used when the range of data is large, requiring data to be grouped into classes that are more than one unit in width.

Categorical Frequency Distribution

A frequency distribution used for data that can be placed in specific qualitative categories, such as nominal-level or ordinal-level data.

Class Midpoint

The value $X_m$ obtained by adding the lower and upper limits (or boundaries) of a class and dividing by $2$.

Histogram

A graph that displays data by using contiguous vertical bars of various heights to represent the frequencies of the classes.

Frequency Polygon

A graph that displays data by using lines that connect points plotted for the frequencies at the midpoints of the classes.

Ogive

Also known as a cumulative frequency graph, it is a graph that represents the cumulative frequencies for the classes in a frequency distribution.