Unit 3 Exploring population and sampling

Population

A researcher wants to study the average screen time of all high school students in California. Since it’s impossible to ask every single student, she instead selects a smaller group. What is the name of the entire group of all California high school students that she ultimately wants information about?

Sample

A researcher surveys 300 high school students in Los Angeles to estimate the average screen time for all California high school students. What is the smaller group called that is actually measured or observed?

Sampling Frame

A professor wants to survey college students about their study habits. He randomly selects names from the college’s official enrollment list, which contains every student at the school. What is the list of all possible subjects that could be chosen called?

Bias

A local newspaper posts an online poll asking readers if they support a new law. Since only people who visit the website voluntarily vote, the results do not represent the opinions of the entire community. What issue is causing the results to be inaccurate?

Simple Random Sample (SRS)

A teacher places the names of all 25 students in a hat and randomly selects 5 names to answer a survey. What sampling method is this, where each individual has an equal chance of being chosen?

Stratified Sample

A school wants to survey 100 students about cafeteria food. To make sure all grade levels are represented, they divide students into groups by grade (freshmen, sophomores, juniors, seniors) and randomly pick 25 students from each group. What sampling method is being used?

Cluster Sample

A researcher wants to survey households in a city. Instead of picking individuals across the whole city, she randomly selects 5 neighborhoods and surveys every household in those neighborhoods. What sampling method is this?

Convenience Sample

A teacher asks the first 10 students who walk into class to complete a survey about homework. What type of sampling method is this, where the sample is chosen based on who is easiest to reach?

Voluntary Response Sample

A radio host asks listeners to call in and give their opinions about a new law. Only people who feel strongly respond, leading to an unbalanced sample. What type of sampling method is this?

Experiment

Scientists want to test if a new fertilizer improves plant growth. They randomly assign some plants to receive fertilizer and others to not receive any, then compare results. What type of study is this, where researchers actively impose treatments?

Observational Study

A doctor studies the link between smoking and lung disease by tracking patients’ health records over 20 years without assigning them to smoke or not. What kind of study is this, where no treatment is imposed?

Confounding Variable

A study finds that children who eat ice cream have better grades. However, it turns out wealthier families are more likely to afford ice cream and also afford better schools. What is the outside factor that affects both variables and confuses the results?

Placebo Effect

In a medical trial, some patients are given sugar pills but still report feeling better because they believe they are taking real medicine. What effect explains this?

Double-Blind Experiment

In a clinical trial, neither the patients nor the doctors know who is receiving the real treatment or the placebo until the study ends. What is this design called, which helps reduce bias?

Random Assignment

A company wants to test two different training programs for employees. They assign workers to each program randomly so results are not influenced by preexisting differences. What process is this, ensuring fairness in experiments?

Control Group

A study tests a new type of workout supplement. One group receives the supplement while another group continues their regular workout with no supplement. What is the name of the group used for comparison?

Replication

Scientists test a new drug on multiple groups of people across several different hospitals to ensure the results are consistent. What principle of experiments does this illustrate?

Census

Instead of sampling, a small school surveys every single student about their lunch preferences. What is it called when data is collected from the entire population?