AP Statistics: Sampling, Random Sampling Methods, What can go wrong

Population

The entire group of individuals we want information about

Census

Collects data from every individual in the population

Sample

A subset of individuals in the population from which we collect data

Choosing a sample

1: Define the population we want to describe
2: Say exactly what we want to measure
3: Decide how to choose a sample from the population

Convenience Sample

Choosing individuals from a population that's easy to reach

How to describe a convenience sample

Edit

Bias

A consistent underestimate or overestimate of the value we want to know

How to describe bias/template

Edit

Voluntary Response Sample

People decide whether to join the sample in response to an open invitation

How describe a voluntary response sample/ template

Edit

Voluntary response vs. Volunteer Sample

Edit

Simple Random Sampling

A sample in which every group of individuals in the population has an equal chance to be selected as the sample

How to take a simple random sample

1: Number the population from (start point) to (end point)
2: Have a stopping point
3: Describe what to do with repeats and value not in range
4: Describe what to do with this group

Template for taking a simple random sampling

Number the (specific population) from (start #) to (end #). Select the first __-digit numbers, rejecting repeats and numbers outside this range. These n context will be in our sample/study.

Stratified Random Sample

A sampling design in which the population is divided into several subpopulations, and random samples are then drawn from each stratum

Reason for using a stratified random sample instead of a simple random sample

We believe the opinions/results of ___ might differ between strata(plausible reason) we want to ensure each strata is represented in the same proportion they are in the population.

How to dscribe reason for taking a stratified sample instead of a SRS/template

Edit

How to take a stratified random sample:

Divide strata n/population x number in sample. Then follow the SRS template and include "Repeat for each strata. Combine these samples from each strata and that will be our sample of n."

Systematic Random Sample

A sample where the items or people are selected according to a specific time or item interval.

Cluster Sample

A sampling design in which entire groups are chosen at random

Reason for using a cluster sample instead of a simple random sample

Taking a SRS would be too time and money consuming AND the population of interest has naturally occurring "mini clusters/populations"

How to describe reason for taking a stratified sample instead of a SRS/template

Edit

How to take a cluster

Divide sample #/ # per section to get amount of sections/clusters. Number all the clusters from __ to ___. Select the first # of clusters __-digit numbers, ignoring repeats and values outside this range. All # per section individuals from each selected cluster will be in our study (n total).

Undercoverage

A sampling scheme that biases the sample in a way that gives a part of the population less representation than it has in the population

Undercoverage Example

Edit

How to describe undercoverage bias/template

Edit

Response Bias

A systematic pattern of incorrect responses in a sample survey

Response Bias Example

Edit

How to describe response bias/template

Edit

Most important influence on the answers given during a survey

The wording of the questions