STATS 1000

Data

collection of numbers, characters, images, etc. that provide info

Data table / data matrix

organized data with cases and variables

Cases

entities on which info is collected (rows of data)

Variables

characteristics we collect from cases (columns of data)

Label

special variable used to distinguish between cases

Categorical variable

responses grouped in categories

Quantitative variable

consists of real #s
measured numerical values

Nominal

ordering does not matter

Ordinal

ordering does matter

Discrete

only take on a set # of values

Continuous

any value & any value between values like 0.5

Population

complete collection of people/objects that a statistician is interested in studying

Parameter

value that describes a characteristic of population

Sample

set of units selected from a population that a statistician analyzes

Statistic

value calculated from sample

Statistical inference

making an educated guess from the statistic on the parameter

Census

sample that consists of the entire population

Representative sample

sample resembles population across all characteristics

Probability Sampling Plan

method of selecting a sample of a population that utilizes some form of random selection

Simple Random Sample

every member of the population has an equal chance of being selected

Systematic Random Sampling

members are sampled according to some predetermined rule by sampling every kth observation

Stratified Random Sample

1. population is divided into groups of similar individuals

2. a simple random is chosen from each group

Cluster Sampling

1. the population first divided into groups

2. simple random sample of the groups are taken

3. every member in the selected cluster becomes part of the sample

Multistage Sample

combines several sampling methods

Bias

any systematic failure of a sampling method to represent its population

Voluntary Response Sample

large group of individuals are invited to respond, and those who choose to respond are counted

Convenience Sample

sample from members who were easiest to access

Undercoverage

some portion of the population is not sampled at all or has a smaller representation

Unresponsive Bias

bias when a large sample fraction fails to respond

Response Bias

anything in the survey design that influences responses