Franc rolled a toy car down a ramp and timed how long it took for the car to reach the bottom of the ramp. After one trial, the student doubled the height of the ramp and added sandpaper to surface of the ramp. He conducted three more trials. After reviewing the data, the student concluded the height of the ramp had no effect on the speed that the car traveled. Which is the most likely reason his conclusion is flawed? * 10 points The student misunderstood how to calculate speed A control should have been included in the investigation Too many variables were changed during the investigation More trials were needed during the investigation

A control should have been included in the investigation  

Explanation:

It is impossible for the student to interpret a correct conclusion about his experiment, without adding a control treatment where he can really compare the differences between the variables.

Control treatment is an element of research that receives all factors, except the variable being tested. The control serves to make comparisons with the other treatments, allowing to observe the exact difference between a system where the variable was tested and the system where it was not.

In the case of the question above, it would have been necessary for the student to have placed a cart on a ramp of normal height and without sandpaper. That way he could compare the speed between this cart and the carts on the other ramps, thus having a correct result.

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