APEX AP Stats 4.2.1 Types of Samples for Surveys Study Guide

What is the primary purpose of a survey?

To draw a conclusion about a population without needing a treatment.

What distinguishes an experiment from a survey?

An experiment uses treatments.

What is a random sample?

A sample where each member of the population has an equal chance of being chosen, selected independently.

What is a simple random sample of size n (SRS)?

A sample where every possible sample of size n is equally likely.

Randomization

a process of randomly assigning subjects to different treatment groups

Why is randomization important in sampling?

It minimizes the effect of confounding variables and allows generalization to the larger population.

What is a representative sample?

A sample that includes characteristics of the population and accurately reflects its diversity.

Is a sample representative if it's random?

no, not necessarily

What does it mean if there is a larger sample size?

there is a greater possibility of the sample being representative to the population

What is a convenience sample?

A sample that is selected non-randomly, often based on ease of access.

What is a stratified random sample?

A sampling method where the population is divided into strata based on shared characteristics, and a random sample is taken from each subgroup.

What are some nuances that are part of the stratified random sample?

1 Each member can only be part of one strata 2. Useful when seeing how the different strata will react 3. Good way to ensure representation if a SRS may not 4. Example of a probability sample

Probability sample

samples that use probability mechanism to assign members to the sample

types of probability samples

1. cluster sample 2. systematic random sample

Strata

subgroup in statistics

Other types of probability samples

1. convenience sample 2. self-selected sample

Should you use convenience and self-selected samples for studies or experiments?

no, they're heavily biased and will not be representative of the population

What is a cluster sample?

A sample where entire groups or clusters are randomly selected, and all or some members of those groups are surveyed.

What is a systematic random sample?

A sample obtained by ordering the population and selecting members using a systematic process.

What is a self-selected sample?

A type of convenience sample where individuals volunteer themselves to participate.

What is the significance of random number generators in sampling?

They provide a method for generating random samples, ensuring unbiased selection.

How can random number tables be used in sampling?

By numbering experimental units and using the first few numbers from the table to select participants.

What is the role of stratification in sampling?

To ensure that different subgroups are adequately represented in the sample.

What does it mean for a sample to be non-probability?

It means the sample is selected in a non-random manner, often leading to bias.

how do you read random number tables?

1. number the amount of experimental units you have, starting from 0 2. take the first 3 numbers of each number in the random number table/split the numbers into chunks on the table 3. look at how many subjects numbers are showing up in the random number table

Successes

numbers or topics that do represent the subject or experimental unit in a random number table