STEP 1 On your own, think about what makes the reasons poor. Base your answer on the examples provided by the students.

STEP 2 Share your ideas and your reasons with your partner.

STEP 3 Listen carefully to your partner’s ideas and reasons.

STEP 4 Together, decide what makes the reasons used to support a conclusion poor. This response might be a mixture of your own and your partner’s ideas and reasons, or just one person’s ideas and reasons.

What makes the reasoning used to support a conclusion poor? Write your answer on your record sheet.

Participate in a class discussion.

Make Sense of Your Ideas

In the previous activities, you learned that an experiment must be a fair test. If it is not, then any conclusion you draw is not valid.

If it is a fair test, you must evaluate the reasons to decide whether the conclusion is valid. The reasons tell how the data (observations) from the experiment actually support the conclusion. Scientists call the data evidence. Data can be collected using any of the five senses or instruments that extend your senses. Examples of instruments include meter sticks, clocks, and thermometers.

In order for their conclusions to be valid, scientists support their conclusions with good reasons. To be good, each supporting reason must meet the following two criteria:

• It must include evidence from the experiment, not an opinion.
• It must use all the available evidence, not just part of the evidence.

If a reason includes an opinion and/or uses only part of the evidence, then the reason is poor, and the conclusion is not valid. Look over the reasons used by students B, C, D, and E on the previous pages.

1. 1. For which student(s) is the reason poor because it includes an opinion, rather than evidence?
2. 2. For which student(s) is the reason poor because it only uses part of the data, rather than all the available data?