The teacher will have each group post their findings from their specific tests (absorbency or strength) on the board for the class to see.

What does our data tell us? Are there differences among the data? Why might the data from different groups be dissimilar? How does your test procedure compare with another groups procedure? What are the similarities or differences of the groups’ testing?

Students may think that everyone tested the same way they did. Some students may not see small inconsistencies in testing (like dropping a gram weight onto the paper towel or placing the gram weight into the paper towel) as an inconsistency.

The teacher will ask students to model some of the procedures of the different groups that could have skewed the results. Drop some weights into the towel while it’s being held tightly, and then place the weight into the towel. Push the towel into the beaker with water, and fold and place the towel into the beaker. The teacher will call on students to describe how the differences in procedure could have affected the results.

How did your group use the gram weights for the strength test? Did everyone use the same kind of placement? Could this have had any effects on your scoring of the different brands of paper towel? Were there any differences during the procedures?

Students may not understand that in an investigation it matters that you keep all variables except one the same. In this instance, the variable is the paper towel.

Scientists, when they are testing a product, like to keep all their testing practices the same so that the tests will be fair for all the paper towels. Introduce the idea of a variable-something that can vary each time a test is done.

Can we decide what we are going to do when we repeat our testing so that we are all doing the same test the same way?

Students may think that the word variable means change and not understand that in scientific testing we strive to control variables except one.

The teacher will instruct the students to perform the tests again, but time each group must agree to a class procedure. The students will determine the methods of testing and the teacher will write the group procedure on the board and the students will begin the testing. All students will record results on the data capture page corresponding to the test they are doing and remember to assign  the point value to each brand of paper towel 1 being the lowest score and 4 being the highest score the towel can get.   Everyone participating in the investigation must perform each test the same way either placing the weight in the paper towel, or dropping it in from a certain height. The teacher will monitor the groups as they begin the second round of testing looking for control of variables, and careful data collection.

What do you think might happen to our results after this round of testing is over? Why do you think so?

Be sure the students understand the scoring system of the test. One is the lowest score and is an indicator of poor performance of the towel on the test and four is the highest score and indicates the best performance on the test.

Post and discuss the new set of data with the students. Allow students to talk about what they saw as the differences between the tests and how those differences affected the results of each trial.

What happened when you performed the absorbency/strength test this time? How do these results compare with the results you obtained before? What was the difference, if any, in your procedure? How would you compare the data from both the first round of testing and the second?

Students may not see differences of 1 or 2 points between the first and second rounds of testing as a problem, and if it doesn’t change the ranking of the towels it may not be. If, however the ranking does change, the students need to see that the point difference is relevant.