Raoul wanted to conduct an investigation to determine what color light is best for plant growth. He predicted that green light will cause tomato plants to grow the tallest. He developed the following steps to conduct his investigation:

 Six identical tomato plants were placed in the same type of container with equal amounts of soil and water.

 He shined one color of light on each of the six tomato plants for the same amount of time each day, using the colors red, orange, green, blue, indigo and violet.

 The height of each plant was measured and recorded at the beginning of the experiment and daily for 50 days.

What essential part of his investigation is missing?

The graph below shows the average growth rate for 50 pairs of newborn rats. One of each pair was treated with a special hormone. The other member of each pair served as a control.

At 70 days, what was the average weight of the rats in the experimental group?

An experiment was set up to test the hypothesis that all plants will grow faster in a "first-class soil" versus regular potting soil. Ten identical plants were tested- five in the "first-class soil" and five in regular potting soil. All plants received the same amount of water, light and fertilizer. Which of the following items would improve the experiment?

Kelsey rolled a marble down a ramp and timed how long it took for the marble to reach the bottom of the ramp. After three trials, she doubled the height of the ramp (making it steeper) and added a thick layer of cotton cloth to the surface of the ramp. She conducted three more trials and after reviewing the data, Kelsey concluded that the height of the ramp had no effect on the speed of the marble rolling down the slope. Which of the following reasons best describes why her conclusion is unsupported?

An engineer is researching the effects of a new safety device for automobiles. He plans to conduct a controlled scientific experiment where he will test a safety device’s effect on being able to survive a high-speed collision. Why is it important to replicate the engineer's experiments?

Luca is comparing the shifts in light patterns of two distant galaxies. Using a powerful telescope, he records the light shifts of each galaxy every 60 seconds (s) for 10 hours (hr). After sharing his data with Julia, another astronomer, she says that this is not an experiment. Which of the following statements supports Julia's claim?

Which of the following statements BEST describes why developing a hypothesis is a very important step in the scientific process?

Zoie wanted to determine if sugar-water affected the growth rate of bean plant seeds. She buried a total of 14 bean plant seeds, each in its own pot with identical soil, and placed the pots in a sunny place. She watered each group of plants with 150 milliliters (mL) of water mixed with a specific amount of sugar. The table below shows the final height in centimeters (cm) of the plants after the experiment was completed.

Jonathan wants to determine the effect of color on the temperature of the air inside of different colored boxes. He places red, yellow, and green boxes of the same size and material in the sunlight, and a thermometer is placed inside each box. He observes and records the temperatures in the boxes at specific times throughout the day. What is the test variable (independent variable) in this investigation?

Magali wants to investigate the effect of mass on a toy car rolling down a ramp. She uses a motion sensor to measure the final speed of the toy car at the bottom of the ramp. Magali begins with an empty toy car, releases it down the ramp and records its speed. She then adds 50 grams (g) of mass to the toy car and measures the car's speed. What is the Outcome Variable (Dependent Variable) in this experiment?

A doctor notices that a vitamin containing Zinc seems to reduce the appearance of acne. Which of the following is the most important step needed in an investigation of the medicine to make a scientifically valid conclusion?

Ruth overheard an automotive technician make this prediction: “This car’s engine will not continue to run for more than 8 minutes." What would be the best reason for saying that the automotive technician’s prediction was scientific?