Algebra 2 Honors - Topic 11 (Statistics)

Statistical question

it can be answered by collecting many pieces of information, or data, and summarizing the data

Statistical variable

a quantity of quality that can be measured or counted, and for which data are expected to differ from one observation to another

Categorical variable

data that falls into categories, used for qualitative data and generally not numerical data

Quantitative variable

a quantity that can be counted

Population

the set of all members of a group you want to know more about

Sample

a subset of the population that is being studied to answer a statical question about the population

Parameter

a measure that describes the entire population

Statistic

a measure that describes a sample of the population

Random sample

a sample selected so that each object/person in the population has an equal chance of being selected and each object/person is chosen independently of any other objects in the sample

Stratified sampling

when a population is divided into groups with similar characteristics and a sample is randomly chosen from each group

Cluster sampling

when a population is divided into convenient clusters, and entire clusters are chosen at random as the sample

Systematic sampling

when you start with one member chosen at random then use a rule, such as “every 3rd member of the population” to select members of the sample

Convenience sampling

only choosing subjects that are in close proximity or easy to get to

Self-selected sampling

using a sample made up of volunteers

Sampling methods with a high risk of bias

convenience and self-selected sampling

Experiment

involves randomly dividing a population into two groups, applying a different treatment to each group, and measuring the difference between the treatments

Sample survey

asks every member of a randomly selected sample the same set of questions and records the answers to try and draw a conclusion about the population

Observational study

you don’t assign treatments to the subjects being studied. The subjects are already affected by the treatments under investigation

How do you identify if a value is an official outlier

value < Q1 - 1.5(IQR) or value > Q3 + 1.5(IQR)