In a headache medicine trial, patients get either the real pill or a sugar pill that looks and tastes the same, and they are not told which one they got. What feature is being used?

A sunscreen study gives one group a lotion with the active chemical and another group a lotion with no active chemical but the same color and smell. What is the second lotion called?

A clinic compares two allergy sprays, but spray A is given only to adults and spray B only to children. What design problem does this describe?

In a pain-relief trial, neither the patients nor the nurse recording pain scores knows who received the real patch. What feature does this describe?

A city tests two traffic-light timing plans. Plan A is used during the summer months, and Plan B is used during the winter months. Which variable is confounded with plan?

A vitamin trial gives one group capsules of inactive powder that look exactly like the vitamin capsules. What role do the inactive capsules play?

A study of tutoring compares an online program used after school with a textbook program used during regular class time. What issue is built into this comparison?

In a blood-pressure study, the technician reading the machine output does not know whether each patient received the new drug or the old drug. What feature is being used?

A school compares two math programs. Program A is taught by veteran teachers, and program B is taught by first-year teachers; class length and time are the same. Which variable is confounded with program?

A clinic compares two exercise plans. Plan A participants also receive weekly coaching calls, while plan B participants receive no calls. Which variable is confounded with exercise plan?

A farm compares two fertilizers. Field A gets fertilizer X and extra irrigation, while field B gets fertilizer Y and normal irrigation. Which variable is confounded with fertilizer?

A sleep study compares a new pillow with a standard pillow. Everyone using the new pillow also sleeps in a cooler room. Which variable is confounded with pillow type?

A website compares two checkout pages. Page A is shown to weekday shoppers, and page B is shown to weekend shoppers. Which variable is confounded with page design?

A hospital compares two recovery plans. Plan A patients are in private rooms, while plan B patients are in shared rooms. Which variable is confounded with recovery plan?

A coach compares two training routines. Routine A is used by varsity athletes, and routine B is used by junior varsity athletes. Which variable is confounded with routine?

In a cold-medicine trial, some patients receive a capsule with no medicine, but it looks like the real capsule. What does this protect the comparison from?

A counselor scoring stress surveys is not told which students used the meditation app. What does this blinding protect the comparison from?

A teacher keeps students from knowing whether they got the new study guide or the old one while they take the same test. What does this blinding protect against?

A nutrition study finds diet A users also exercised more than diet B users. Why is exercise a problem for the comparison?

In a skin-cream trial, both creams are packaged alike so neither users nor evaluators know which cream is active. What does this mainly protect against?

In a sleep-pill trial, patients are not told whether they got the pill or a look-alike capsule, but the doctor scoring sleep diaries is told. Who is blinded?

In an eye-drop trial, patients know whether they got the new drops, but the technician measuring redness does not know. Who is blinded?

In a bandage trial, patients cannot tell which bandage they received, and the nurse judging healing photos also does not know. Who is blinded?

In a running-shoe study, athletes are told which shoe model they wear, and the coach timing the race also knows. Who is blinded?