AP Statistics Flashcards: Random Sampling and Data Collection
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 19 cards to help you master important concepts.
A student puts the names of all 25 students in his class into a hat, mixes them up, and draws 5 names. Identify the sampling method.
This is a simple random sample (SRS) because every group of 5 students has an equal chance of being chosen.
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A student puts the names of all 25 students in his class into a hat, mixes them up, and draws 5 names. Identify the sampling method.
This is a simple random sample (SRS) because every group of 5 students has an equal chance of being chosen.
Explain why a systematic random sample might not be appropriate if there is a recurring pattern in the population list.
If the sampling interval aligns with a pattern in the list (e.g., every 10th house is a corner lot), the sample could be biased by over- or under-representing that characteristic.
What is a Simple Random Sample (SRS)?
An SRS is a sample where every group of a given size has an equal chance of being chosen from the population.
A polling company wants to survey voters in a large county. They randomly select 10 voting precincts from 150 total and interview every registered voter in those 10 precincts. What method is this?
This is a cluster sample because the population was divided into clusters (precincts), a random sample of clusters was chosen, and all individuals in those clusters were surveyed.
What is a major advantage of cluster sampling compared to a simple random sample (SRS)?
Cluster sampling is often more practical, cheaper, and faster than an SRS, especially when the population is spread over a wide geographic area.
What is the defining characteristic of the groups (strata) in a stratified random sample?
The strata are homogeneous groups, meaning the individuals within each stratum share a similar characteristic of interest to the researcher.
Define 'sampling with replacement'.
Sampling with replacement is a method where an item can be selected multiple times because it is returned to the population after each selection.
Is there one sampling method that is always the best to use?
No, each sampling method has its own advantages and disadvantages. The best method depends on the specific situation, the population being studied, and the resources available.
A lottery machine contains 50 numbered balls. For the final prize, one ball is drawn and not put back in before the next draw. Is this sampling with or without replacement?
This is sampling without replacement because once an item (a numbered ball) is selected, it can only be selected once and is not returned to the population.
A principal wants to know the opinion of all 75 teachers at her school about a new policy. She decides to email the survey to every teacher. What data collection method is she using?
This is a census because she is collecting data from all subjects in the entire population of teachers at her school.
Define 'sampling without replacement'.
Sampling without replacement is a method where an item from a population can be selected only one time.
To check the quality of a shipment of 1,000 lightbulbs, a factory manager randomly selects a starting bulb from the first 20 on the line and then tests every 20th bulb thereafter. What method is this?
This is a systematic random sample because it selects members from a population at a fixed interval from a random starting point.
Why would a researcher choose a stratified random sample over a simple random sample (SRS)?
A researcher would choose a stratified sample to ensure that specific subgroups (strata) of the population are adequately represented in the sample, which can lead to more precise estimates for each subgroup.
What is a Cluster Sample?
This method involves dividing a population into clusters, randomly selecting some of those clusters, and then collecting data from all individuals within the chosen clusters.
What is the key difference between how individuals are selected in a stratified sample versus a cluster sample?
In a stratified sample, individuals are randomly selected from *all* groups (strata), whereas in a cluster sample, *all* individuals are taken from a random selection of groups (clusters).
What is a Stratified Random Sample?
This method involves dividing a population into homogeneous groups called strata and then taking a simple random sample from each stratum.
A researcher wants to survey 200 high school students. They divide the students by grade level (freshman, sophomore, junior, senior) and randomly select 50 students from each grade. What method is this?
This is a stratified random sample because the population was divided into homogeneous groups (strata) by grade level before random sampling occurred within each group.
What is a census?
A census is a data collection method that selects and gathers information from all items or subjects in a population.
What is a Systematic Random Sample?
This method selects members from a population at a fixed periodic interval, starting from a randomly determined point.