Scientific Method

Farmer Bill wants to know if alfalfa hay will cause a cow to produce more milk than regular hay. He divides his herd into two groups of 40. He feeds each member of one group 50 pounds of alfalfa hay each day and the other group 50 pounds of regular hay each day. He uses the same breed of cattle and gives them the same amount of water. He measures the gallons of milk produced per cow each day.

What is the independent variable in the experiment above?

• amount of milk

• amount of alfalfa hay

• the cows that receive the alfalfa hay

• the cows that receive regular hay

Ryan grew up watching his grandmother place teabags around her rose bushes in the spring. She claimed it made her rose bushes produce more flowers. Now Ryan has decided to test this hypothesis in his science fair project.

Which of the following is the most valid way for Ryan to set up this experiment?

• Have two groups of roses - one with fertilizer and one without. Give both groups equal amounts of water, teabags, and sunlight, and count how many roses are produced by each group.

• Have two groups of roses - one with tea bags and one without teabags. Keep water, sunlight, and fertilizer equal between the two groups and count how many roses are produced by each group.

• Have three groups of roses – one with fertilizer but no teabags, one with teabags but no fertilizer, and one with neither teabags or fertilizer. Give both groups equal amounts of water and sunlight.

• Have just one group of roses, and place tea bags around them. Give them water and sunlight, and count how many roses are produced.

Scientists perform an experiment to test the effect of sunlight intensity on the growth of kudzu. What is the independent variable in this experiment?

• the scientists

• the growth of the kudzu

• sunlight intensity

• fertilizer and water

Scientists think magnesium helps relieve minor pains. The scientists’ belief is best described as which of the following?

• a hypothesis

• a theory

• a scientific law

• a problem

Sarah wants to observe the effects of fertilizer on corn growth. She plants four rows of corn. Row 1 receives 0 grams of fertilizer. Row 2 receives 20 grams. Row 3 receives 30 grams. Row 4 receives 40 grams. At the end of the experiment, she records the height of each stalk. How many grams of fertilizer did the control group receive?

• 0

• 20

• 30

• 40

Sarah wants to observe the effects of fertilizer on corn growth. She plants four rows of corn. Row 1 receives 0 grams of fertilizer. Row 2 receives 20 grams. Row 3 receives 30 grams. Row 4 receives 40 grams. At the end of the experiment, she records the height of each stalk. What is the independent variable?

• fertilizer

• the type of corn used

• the height of the corn stalks

• the water and sunlight

Sarah wants to observe the effects of fertilizer on corn growth. She plants four rows of corn. Row 1 receives 0 grams of fertilizer. Row 2 receives 20 grams. Row 3 receives 30 grams. Row 4 receives 40 grams. At the end of the experiment, she records the height of each stalk. What is the dependent variable?

• fertilizer

• the type of corn used

• the height of the corn stalks

• the water and sunlight

Sarah wants to observe the effects of fertilizer on corn growth. She plants four rows of corn. Row 1 receives 0 grams of fertilizer. Row 2 receives 20 grams. Row 3 receives 30 grams. Row 4 receives 40 grams. At the end of the experiment, she records the height of each stalk. Which of the following would NOT be the same for each group?

• the amount of fertilizer

• the type of corn used

• amount of water

• the type of soil

John performed an experiment to test the effects of soap on bacterial growth. He set up four petri dishes with nutrient agar and bacterial cultures. He placed a different type of soap in three of the dishes and left one dish with no soap. Finally, he compared the bacterial growth in the petri dishes after three days of incubation.

What is the independent variable of John's experiment?

• bacterial growth

• nutrient agar

• type of soap

• petri dish with no soap

Angela wants to know if increasing the amount of pesticide in a garden will cause corn stalks to produce more corn.

If she sets up an experiment to test this, what will be the independent variable?

• corn stalks without the pesticide

• amount of corn produced

• amount of pesticide

• the soil in the garden