4.1 Vocabulary AP Statistics

Population

In a statistical study is the entire group of individuals we want information about

Census

collects data from every individual in the population

Sample

is a subset of individuals in the population from which we actually collect data

Sample Survey

for studies that use an organized plan to choose a sample that represents some specific population.

Convenience Sample

is a sampling method that involves choosing individuals from the population who are easy to reach. It is generally biased because they don’t really represent the entire population.

Bias

is shown in a statistical study when it consistently underestimates or overestimates the value you want to know. Bias is the tendency for a sample to differ from the corresponding population in some systematic way. Some part of the population is systematically favored over another part.

Voluntary Response Sample

consists of people who choose themselves by responding to a general invitation. They are generally biased as they over represent people with strong opinions.

Random Sampling

involves using a chance process to determine which members of a population are included in the sample. **Larger random samples typically give better information about the population than smaller samples

Simple Random Sample (SRS)

of size n is chosen in such a way that every group of n individuals in the population has an equal chance to be selected as the sample. An SRS also gives each member of the population an equal chance to be included in the sample.

Random Number Table

is a table of random digits and can be used to choose individuals randomly.

Stratified Random Sample

starts by classifying the population into groups of similar individuals, called strata. Then choose a separate SRS in each stratum and combine these SRSs to form the sample. **”Some from all”

Cluster Sample

starts by classifying the population into groups of individuals that are located near each other, called clusters. Then choose an SRS of the clusters. All individuals are included in the sample. **”All from some”

Inference

is the process of drawing conclusions about a population on the basis of simple data

Undercoverage (Selection Bias)

occurs when some members of the population cannot be chosen in a sample.

Nonresponse Bias

occurs when an individual chosen for the sample cannot be contacted or refuses to participate.

Response Bias

occurs when inaccurate answers are given in survey questions. Some reasons are wording of the question, appearance of the interviewer, asking about illegal behavior, unpopular beliefs, past events, taking measurements