AP Stats Collecting Data Vocab

Popoulation

the entire group we want information about

Sample

A part of the population we examine to get info

Census

Collects data from every individual in the population

Observational Study

Observe individuals and measure variables of interest but do not attempt to influence the responses

Experiment

deliberately omposes some treatment on individuals to measure their responses

Convenience Sampling

Uses subjects that are readily available

Voluntary Response Sample

Obtained by allowing subjects to decide whether or not to respond (self-selected survey)

Simple Random Sample (SRS)

n individuals from population are chosen in a way that every set of those n individuals has an equal chance of being selected to be in the sample

Stratified Random Sampling

Divide the population into groups of similar individuals (strata) then select an SRS within each strata and combine them to form a sample

Cluster Sampling

Dvide the population sections (clusters) then randomly choose a few clusters to become part of your sample

Systematic Random Sampling

Randomly selects an arbitrary starting point and then select every kth member of the population

Without Replacement

When an item from a population can be selected only once

With Replacement

When an item from the population can be selected more than once

Biased

If they are systematically not representative of the desired population

Voluntary Response

When a sample is comprised entirely of volunteers or people who choose to participate, the sample will typically not be representative of the population (volunteer response bias)

Undercoverage

Occurs when some groups in the population are left out of the process of choosing a sample

Non-Responsive

Occurs when an individual chosen for a sample can’t be contact or refuses to respond. Non-response is a big problem in mail surveys

Response Bias

Bias caused by the behavior of the respondent or interviewer

Caused by the following:

Untruthful Answers

Ignorance

Lack of Memory

Timing

Phrasing

Sampling Error

The difference between a sample result and the true population result. This error results from chance variation (not a mistake)

Non-Sampling Error

Occurs when the sample data are incorrectly collected, recorded, or analyzed. Usually happens when the sample is selected in a non-random fashion.