Flashcards AP Stats: Collecting Data

Population

the entire group of individuals we want information about

Parameter

a number that describes some characteristic of the population

Census

collects data from every individual in the population

Sample

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

sample survey

A study that collects data from a sample that is chosen to represent a specific population

convenience sample

Sample selected by taking from the population individuals who are easy to reach

Bias

The design of a statistical study shows this if it is very likely to underestimate or very likely to overestimate the value you want to know

voluntary response sample

A sample that consists of people who choose to be in the sample by responding to a general invitation

random sampling

involves using a chance process to determine which members of a population are included in the sample

simple random sample (SRS)

Sample chosen in such a way that every group of n individuals in the population has an equal chance to be selected as the sample

Strata

groups of individuals in a population who share characteristics thought to be associated with the variables being measured in a study

stratified random sampling

selects a sample by choosing an SRS from each stratum and combining the SRSs into one overall sample

Cluster

A group of individuals in the population that are located near each other

cluster sampling

Selects a sample by randomly choosing clusters and including each member of the selected clusters in the sample

Undercoverage

occurs when some members of the population are less likely to be chosen or cannot be chosen in a sample

Nonresponse

occurs when an individual chosen for the sample can't be contacted or refuses to participate

response bias

Occurs when there is a systematic pattern of inaccurate answers to a survey question

statistic

a number that describes some characteristic of a sample

Survey

an investigation about the characteristics of a given population by means of collecting data from a sample of that population and estimating their characteristics through the systematic use of statistical methodology

Random digit table

A chance device that is used to select experimental units or conduct simulations.

study versus experiment

In an experiment, you control the variables. In an observational study, you use natural conditions. An experimental study involves a hypothesis and a variable. An observational study is simply a set of observations without a hypothesis or a variable.

Systematic sampling

sample members from a larger population are selected according to a random starting point and a fixed periodic interval

inference for sampling

the process of drawing conclusions about a population on the basis of sample data

margin of error

The difference between the point estimate and the true parameter value will be less than the margin of error in C% of all samples, where C is the confidence level.

question wording

the way in which survey questions are phrased, which influences how respondents answer them

Probability sample

a sample in which every element in the population has a known statistical likelihood of being selected