A group of students is trying. to determine which detergent will best remove an oil stain. They stain five separate cloths with oil and. then wash each of. the cloths in a deficient detergent. They repeat each test two more times. Which step should be included in their investigation plan?

The group of students should have stained separate but identical pieces of cloth.

There are different factors that influence how easily a stain will come out of a material such as:

Assuming the temperature is held constant and the type of detergent is being tested, the only thing other thing to control is the type of material.

The students used separate cloths instead of identical ones which meant that a significant variable was not controlled.

In conclusion, the students should use separate but identical pieces of cloth so that the type of material would not impart their experiment.

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