Pick Your Sample
This type of sample occurs when members of a population choose to participate, such as responding to a Yelp review or an online poll.
self-selected sample
This method involves investigating one or more characteristics of a population by asking a sample of people questions.
survey
These are errors that misrepresent a population, often caused by the way a sample is chosen or how questions are worded.
bias
This is the first step in any statistical study.
identifying the variable of interest and the population
You want to know what people think of a new movie, so you interview the first 20 people who walk out of the theater because they are easily reached. Name the sampling type.
convenience sampling
A researcher uses a specific rule to select members, such as choosing every 10th person who walks into a store
a systematic sample
A researcher stands at a gas station and records how many people choose diesel versus regular gasoline without talking to the drivers.
observational study
"Do you agree that our cafeteria should switch to healthier options?" Why is this question flawed?
It is a biased question because it encourages a "yes" response/leads the respondent
On a TI-84 calculator, you use this command to generate random integers to help minimize bias
randInt
A medical researcher wants to test a new drug. They give the drug to Group A and a placebo to Group B. This is an example of what?
experiment
To ensure every grade level is represented, a principal divides the school into freshmen, sophomores, juniors, and seniors, then randomly picks 20 students from each group.
stratified sample
A teacher allows one class to use calculators on a test while another class cannot, in order to see if it affects their scores.
an experiment (imposing a treatment)
A math teacher asks their 1st-period class if the whole school wants more quizzes. Why is this biased?
It is convenience sampling and does not reflect the entire population (other classes couldn't participate)
What is the difference between a population and a sample?
A population is the entire group being studied, while a sample is a subset used to represent that group
Rewrite this biased question to be neutral: "Don't you think the city should spend more money on beautiful parks?"
"Should the city increase spending on parks?" (Removing "don't you think" and "beautiful")
A population is divided into groups based on physical location, and the researcher randomly selects entire groups to sample.
cluster sample
Because it would be too dangerous or impractical to crash real cars repeatedly, engineers use a computer model to predict safety outcomes.
simulation
Give an example of a "sensitive" question flaw in a survey.
A question that is too personal or embarrassing for the respondent to answer truthfully
If the odds of winning a prize are 3/5, what is the actual probability of winning?
3/8 or 37.5%
A quality control manager wants to check lightbulbs. He tests every 50th bulb on the assembly line. Which sampling method is this?
systematic sampling
A student lists all peers alphabetically and chooses every 6th student. Identify the sampling method and one potential drawback.
systematic sampling
Identify the method: A scientist uses a computer to model possible vote projections for an upcoming election.
simulation
A news organization asks viewers to participate in an online poll. Name the sampling type and one reason it is biased.
self-selected sampling (Bias: Only people with internet access and a strong opinion will respond)
List the five steps of a statistical study in order.
1. ID variable/population; 2. Choose a representative sample; 3. Collect data; 4. Organize/describe data; 5. Interpret/draw conclusions
To determine if students like the school website, a researcher randomly selects 2 students from every classroom in the building. Name this sampling method.
stratified sampling (strata=classroom)