A prediction can fit the results you already have and still need a new test.

In a fair bean test, 40, 80 and 120 mL daily gave heights of 3, 9 and 6 cm after two weeks. Which prediction for 100 mL daily uses the nearby results without claiming certainty?

• The plant might finish between 6 and 9 cm tall
• The plant must finish exactly 20 cm tall, whatever happens in the new test
• The plant must finish below 3 cm because every increase in water makes plants shorter

Ben wants to compare daily water amounts of 80, 100 and 120 mL in a follow-up bean test. Which plan fairly compares those amounts?

• Use several beans per amount, but choose a different bean type for each water amount
• Use several similar beans per amount and keep other conditions the same
• Use several beans per amount, but give the 100 mL group larger pots and more light

Maya predicts that her paper plane with 3 clips will fly about 2 m. She wants to compare 2 and 3 clips. Which follow-up keeps other conditions the same?

• Use the same plane, clip position, thrower, launch method and indoor space
• Use the same plane and indoor space, but ask another person to throw much harder with three clips
• Use the same thrower and launch method, but reshape the wings and move outdoors with three clips

An adult tested equal-sized ice cubes under the same conditions except room temperature. At 10, 20 and 30 degrees C, melting took 18, 12 and 8 minutes. What could happen at 35 degrees C if the pattern continues?

• The cube must melt in exactly four minutes, even without a new test
• The cube may take longer than eighteen minutes as the temperature rises
• The cube may melt in less than eight minutes

Ben predicted that a plant would be between 8 and 12 cm tall after two weeks. It measured 7 cm after the planned two weeks. What should he conclude?

• This proves that no plant given that amount of water can ever reach eight cm
• This result is outside his predicted range; check the test and repeat
• This confirms his prediction because seven cm is close to the lower limit of eight cm

In a fair ramp test, heights of 10, 20 and 30 cm gave toy-car roll distances of 15, 30 and 45 cm. If this number pattern continues, what distance would you predict for a 40 cm ramp, in cm?

Ben compares 200 mL daily with 150 mL daily, but also gives the 200 mL group bigger pots and more light. Why can this comparison not separate the effect of water amount?

• Because every follow-up must use the largest water amount from the earlier test
• Because bigger pots stop the water amount from affecting any plant's growth
• Because water, pot size and light changed together