The Scientific Method - Experimental Variables.

A scientist performs an experiment to see if acids have an effect on the health of a particular type of plant. Three sets of plants were treated with acidic solutions of known pH while the control set was treated with a solution of neutral pH 7.Which is the best conclusion for this experiment?

• Acid has no effect on the health of this type of plant.
• B. High acidity is helpful to this type of plant.
• C. Low acidity is harmful to this type of plant.
• High acidity is harmful to this type of plant.

The graph below shows atmospheric carbon dioxide levels since the year 1880.Which of the following conclusions can be drawn from this graph

•  Atmospheric carbon dioxide levels are responsible for global temperature change.
•  Atmospheric carbon dioxide levels have been rising at about the same rate for the past century.
• Atmospheric carbon dioxide levels have remained the same over the past century.
•  Atmospheric carbon dioxide levels have been rising at an increasingly higher rate as the past century has progressed.

Carmen conducted an experiment to determine if listening to different types of music would affect a person’s pulse. Her hypothesis was that pulse rate would change with different types of music. Each person listened to seven different selections of music for 30 seconds each. Each person’s pulse was taken before the music and then after each 30-second interval of music. The pulses were taken again after the music selections were completed. Based on her experiment, Carmen concluded that a person’s pulse rate changed when the person listened to different types of music.  Which component is missing from Carmen’s experiment?

• a question
• a hypothesis
• a control group
• a description of the experiment

In an appropriately designed experiment, a scientist is able to test the effect of

•  a single variable
•  multiple variables
•  the hypothesis
•  scientific observations

Which statement best expresses a basic scientific assumption?

• Interpretation of experimental results has provided explanations for all natural phenomena.
• If a conclusion is valid, similar investigations by other scientists should result in the same conclusion.
• For any conclusion to be valid, the design of the experiment requires that only two groups be compared.
• After a scientist formulates a conclusion based on an experiment, no further investigation is necessary.

An experiment was carried out to determine whether drinking caffeinated soda increases pulse rate. The pulse rates of two groups of people at rest were measured. Group A was then given caffeinated soda and group B was given caffeine-free soda. One hour after drinking the soda, the pulse rates were measured. The participants in the experiment were all the same age, and they were all given the same amount of soda. The dependent variable in this experiment is the

• type of soda given to each group
• amount of soda given to each group
•  pulse rate of each group
• age of participants in each group

A series of steps used by scientists to solve a problem or answer a question. 

• scientific method
• recipe
• data collection
• metric system

There are two types of data. Which type of data involves numbers that are obtained by counting or measuring?

• quantitative
• qualitative

When experimenting with the growth of a plant, a scientist uses three (of the same type of) plants, two different fertilizers, equal light, and equal water. What type of variable is the fertilizer?

• Dependent
• Independent
• Control
• Compound

Research Question: Does the type of gasoline put in a car effect how fast the car can drive. What is the independent variable?

• Type of gasoline
• which car the gas is put into
• how fast the car can drive
• how much gas is put into the car