Researchers randomly assign 90 students to use either a new study app or their usual notes, then compare quiz scores. What kind of study is this?

A city emails residents asking which park they visit most often. No treatment is imposed. What kind of study is this?

A researcher records how many hours teens sleep and their math grades. The teens choose their own sleep schedules. What kind of study is this?

A nutritionist randomly assigns volunteers to drink either 500 mL of water or 500 mL of a sports drink before exercising, then records endurance. What kind of study is this?

A school asks every tenth student entering the cafeteria to answer questions about lunch satisfaction. No treatment is assigned. What kind of study is this?

A hospital compares recovery times for patients whose doctors already chose surgery or physical therapy. The hospital does not assign treatments. What kind of study is this?

An online poll asks shoppers whether they prefer paper or digital receipts. The poll only records answers. What kind of study is this?

A botanist randomly assigns identical plants to receive 6 hours or 10 hours of light each day, then measures growth. What kind of study is this?

A data team records the commute distance and arrival time of employees who chose where to live. No one is assigned a commute. What kind of study is this?

A teacher asks students to rate homework difficulty on a form after a unit test. No study method is assigned. What kind of study is this?

A coach randomly assigns runners to two training plans for eight weeks, then compares 5 km times. What kind of study is this?

Researchers compare screen time and sleep quality using phone records from volunteers who chose their own habits. What kind of study is this?

A pharmacy randomly gives patients either a new reminder text or no reminder, then compares prescription pickup rates. What kind of study is this?

A wildlife team counts birds in wetlands with and without nearby roads. The roads already exist, and no habitat is assigned. What kind of study is this?

Adults who already exercise at least 150 minutes weekly have lower resting heart rates than adults who do not. No treatment was assigned. What conclusion is supported?

A random sample of voters is asked whether they support a bond issue, and 58% say yes. What conclusion is supported?

A trial randomly assigns patients to a new cream or a placebo cream, then compares rash size after one week. The new cream group improves more. What conclusion is supported?

Students who choose online tutoring score higher on average than students who do not. The school only records choices and scores. What conclusion is supported?

A company randomly assigns call centers to a new script or the old script, then compares customer ratings. The new script group rates higher. What conclusion is supported?

A survey asks a random sample of households how many streaming services they pay for. The sample mean is 2.4 services. What conclusion is supported?

Researchers observe that neighborhoods with more trees have lower summer pavement temperatures. Cities chose their own tree planting. What conclusion is supported?

A lab randomly assigns 80 seedlings to fertilizer A or fertilizer B and finds fertilizer A produces taller plants. What conclusion is supported?

A survey of a random sample of seniors finds 72% plan to attend graduation. What conclusion is supported?

A restaurant records that customers ordering from a digital menu spend more than customers using paper menus. Customers choose their menu type. What conclusion is supported?

In a study, 100 volunteers are randomly split. One group hears white noise while studying; the other hears silence. All take the same memory test. What is the treatment?

A trial randomly assigns plants to receive compost tea or plain water, then measures height after four weeks. What is the response variable?

Researchers randomly assign classrooms to use new desks or standard desks, then compare on-task minutes. Which group is the control group?

A company randomly assigns employees to receive a wellness email every morning or no email, then records sick days. What is the treatment?

In a randomized experiment, one group uses a 15-minute meditation app daily, and one group uses no app. Stress score is recorded after 30 days. What is the response variable?

A drug trial randomly assigns patients to a new medicine or an identical pill with no active ingredient. Which group is the control group?

A school randomly assigns bus routes to send arrival reminder texts or no texts, then records late arrivals. What is the treatment?

An experiment randomly assigns fish tanks to blue light or white light and records algae mass after two weeks. What is the response variable?

A principal wants to estimate the percent of all students who want later start times, without making a cause-and-effect claim. What design should the principal use?

A bakery wants to know whether a new package design causes higher cookie sales. What design supports that claim?

A researcher wants to study the relationship between daily caffeine intake and sleep quality without assigning caffeine amounts. What design should be used?

A park manager wants public opinions on adding a bike path. The goal is to estimate support among residents. What design should be used?

A coach wants to test whether stretching for 10 minutes causes faster sprint times. What design should the coach use?

A scientist wants to examine whether river nitrate level is associated with algae mass, without changing any rivers. What design should be used?

A phone company wants to claim that a new app layout reduces checkout time. What design supports that claim?

A district wants to estimate the average number of minutes students spend on homework each night. What design should be used?