A school garden tests three fertilizers on 45 bean plants, assigning 15 plants to each fertilizer and recording plant height in centimeters after six weeks. What are the treatments?

A coach assigns 30 runners to stretch for 5, 10 or 15 minutes before practice, then measures each runner's 400-meter time. Identify the treatments in this experiment.

A clinic gives 90 patients one of three reminder methods: text message, phone call or no reminder, then records whether each patient attends an appointment. What are the treatments?

A cafeteria tests two tray designs with 200 students, randomly giving each student one tray type and measuring grams of food wasted. Which part names the treatments?

A farmer assigns 36 plots to receive 0, 2 or 4 liters of compost tea each week and records tomato yield in kilograms. What are the treatments?

A teacher tests math apps by assigning 72 students to App A, App B or paper practice for four weeks, then giving the same quiz. Which are the treatments?

A lab tests fabric softeners by washing 60 cotton towels with brand X, brand Y or no softener, then rating softness. Name the treatments.

A wildlife center assigns 24 injured birds to one of two diets, standard seed mix or seed mix with extra protein, and measures mass gain in grams after a month. What are the treatments?

A dermatologist tests two lotions on 50 volunteers, assigning each volunteer one lotion for eight weeks and measuring skin dryness. What are the experimental units?

A nursery compares light levels by placing 40 seedlings under low, medium or high light and measuring leaf area. Identify the experimental units.

In a tire study, 48 identical tires are assigned to three tread compounds and driven until tread depth is measured in millimeters. What are the experimental units?

A music teacher assigns 64 students to practice with a metronome or without one for 12 days, then records accuracy scores. Which are the experimental units?

A factory applies four paint coatings to 80 metal panels, one coating per panel, then measures rust area in square centimeters after salt spray. Name the experimental units.

A veterinarian assigns 30 dogs to two flea treatments and counts fleas after three weeks. What are the experimental units in the experiment?

A paper company tests drying temperatures by making 36 sheets at 80 °C, 90 °C or 100 °C and measuring sheet strength. Identify the experimental units.

A dentist assigns 100 patients to a new mouthwash or a standard mouthwash for three months, then counts plaque spots. What is the response variable?

A school tests seat height by assigning 45 students to desks at three heights and recording typing speed in words per minute. Which is the response variable?

A greenhouse assigns 54 rose bushes to misting once, twice or four times daily, then measures bloom count after a month. Name the response variable.

A doctor gives 120 adults either a sleep app or no app for two weeks and records average nightly sleep in hours. What is the response variable?

A car wash tests three soap mixtures on 30 cars and rates paint shine after washing. Which item is the response variable?

A reading specialist assigns 80 children to two vocabulary games and measures words learned on a 20-word test. Identify the response variable.

A phone company assigns 70 batteries to fast charging or regular charging, then measures battery life in hours after 100 cycles. What is the response variable?

A hospital tests a pain medicine by giving 60 patients the medicine and 60 patients a look-alike pill with no active drug, then recording pain scores. Which group is the control group?

A company studies an energy drink by giving 40 workers the drink and 40 workers a same-tasting drink without caffeine, then measuring alertness. Identify the control group.

A dog trainer compares a new training collar with a standard collar, assigning 25 dogs to each and counting commands followed. What is the control group?

A sunscreen lab gives 35 volunteers a new sunscreen and 35 volunteers the current sunscreen, then measures redness after UV exposure. Which group serves as the control group?

A teacher tests a new homework policy by having one class use it while another similar class keeps the old policy, then comparing quiz scores. Which is the control group?

A lab tests whether added sugar speeds yeast growth by giving 20 flasks sugar solution and 20 flasks plain water, then measuring gas volume. Name the control group.

A researcher lets students choose whether to use a new study app or their usual notes, then compares exam scores. Which design principle is missing?

A farmer flips a coin to choose which of two nearby corn plants gets a new pesticide, leaves the other plant untreated, then compares insect damage. What design principle is missing?

A lab gives every mouse a new vitamin mix and records weight gain, with no mice receiving the regular diet alone. Which principle is missing?

A teacher flips a coin to assign one student to online tutoring and one student to in-person tutoring, then compares test gains. Which design principle is missing?

A clinic assigns the first 30 arrivals to a new therapy and the next 30 arrivals to standard therapy, then measures pain reduction. Which principle is missing?

A coach puts all 20 swimmers on a new workout for a month and compares their race times to their old times, with no usual-workout group. Which principle is missing?

A botanist randomly assigns 12 plants to a new lamp and 12 to a standard lamp, then measures growth. All 24 plants sit on the same shelf. Which statement about the design is correct?

A chef bakes one loaf with a new bread recipe and one loaf with the old recipe, using a coin flip to decide which to bake first, then rates taste. Which principle is missing?

A phone maker gives every test phone a new screen coating and records scratch depth, but no phones receive the current coating. Which principle is missing?

A store manager assigns cashiers with even employee numbers to a new checkout script and odd numbers to the old script, then times transactions. Which principle is missing?

A biologist tests a water additive in 10 fish tanks and measures fish growth, but every tank receives the additive. Which principle is missing?

A principal lets teachers volunteer their classes for a new reading program, while nonvolunteer classes keep the old program, then compares reading scores. Which principle is missing?