Experimental design

Which of the following statements best describes a controlled experiment?

• It tests 2 variables at a time

• it always has a control group

• the experiment is carried out only 1 time

• it tests the effect of 1 dependent variable

In an experiment, the variable that you are testing is called the

• control variable

• dependent variable

• independent variable

• the constant

An if......then statement that can be tested by a scientist is called a(n)

• hypothesis

• theory

• conclusion

• inference

In an experiment the data that you are collecting can also be called the

• independent variable

• dependent variable

• manipulated variable

• conclusion

Which of the following would be a way to increase the validity of an experiment?

• repeat the experiment several times

• use only a few test subjects

• do the experiment once

• Borrow data from another scientist

When graphing data, the independent variable will always be placed on ___________

• the Y-axis

• the title of the graph

• in the key

• the X-axis

Observations can be collected as data. Observations that describe the qualities of an object are called

• quantitative observations

• inferences

• qualitative observations

• none of the above

When you make a conclusion based upon observations and data you have collected, it is called a(n)

• inference

• conclusion

• analysis

• hypothesis

A student hypothesized that lettuce seeds would not germinate (begin to grow) unless they were covered with soil. The student planted 10 lettuce seeds under a layer of soil and scattered 10 lettuce seeds on top of the soil. The data collected are shown in the accompanying table. Data Table Seed Treatment Number of Seeds Germinated Planted under soil 9 Scattered on top of soil 8

To improve the reliability of these results, the student should.....

• conclude that darkness is necessary for lettuce seed germination

• conclude that light is necessary for lettuce seed germination

• revise the hypothesis

• repeat the experiment using a larger sample size

Which statement about the use of independent variables in controlled experiments is correct?

• A different independent variable must be used each time an experiment is repeated

• The independent variables must involve time.

• Only one independent variable is used for each experiment.

• The independent variables state the problem being tested.