Statistics Unit 1

Population

Population

All individuals or things

Parameter

A characteristic or constant factor, limit

Sample

A subset/ group of the population

Inferential statistics

numerical data that allows predictions - to infer from sample data the probability of something being true of a population. ex: The estimate population of USA in 2050

Descriptive statistics

Statistics that summarize the data collected in a study. ex: the population of USA the last 10 years

Quantitative data

Numerical data (numbers)

Qualitative data

Information describing color, odor, shape, or some other physical characteristic

Discrete data

Whole number, can't be a decimal

Continuous data

Data that can take on any value. ex: decimals (2.5, 10.75)

Nominal data

Data of categories only. Data cannot be arranged in an ordering scheme. (Gender, Race, Religion)

Ordinal data

Data exists in categories that are ordered but differences cannot be determined or they are meaningless. (Example: 1st, 2nd, 3rd)

Interval data

Differences between values can be found, but there is no absolute 0. (Temp. and Time)

Ratio data

data with an absolute 0. Ratios are meaningful. (Length, Width, Weight, Distance)

Simple Random sampling

Pick sample randomly from a list. Every member of the population has a known and equal chance of selection.

Systematic sampling

A sample drawn by selecting individuals systematically. Such as every 4th.

Stratified sampling

Population is divided into sub-groups, then a sample is taken from each in proportion to the population size

Clustered sampling

Divides the population into even groups and randomly selects a number of these groups for sampling. Choose whole groups randomly

Experimental Study

The researcher manipulates one of the variables and tries to determine how the manipulation influences other variables

Observational Study

Observes individuals and measures variables of interest but does not attempt to influence the responses

Survey Study

A study of people's responses to standardized questions

Independent Variable

The variable being manipulated by the researcher in an experimental study.

Dependent Variable

The resultant variable in an experimental study.

Response variable

The variable being measured and is the result of the treatment.

Explanatory Variable

The treatment being given to test subjects (whether given naturally or by the researcher).

Treatment Group

The group in the study that received the special instruction.

Control Group

The group that had no special instruction.

Placebo

is anything that seems to be a "real" medical treatment -- but isn't. It could be a pill, a shot, or some other type of "fake" treatment.