Danny wants to improve his technique for punting the football, so he devises an experiment to help. He goes to the field with 5 different kinds of shoes, thinking that with his experience level, the type of shoe might make a difference. He kicks the ball 10 times with each shoe and measures the distance it went. He uses 3 types of shoes on Monday, but because it got dark earlier than expected, has to complete the test on Tuesday. What is a major change Danny should make, to increase the validity of his test?

A) do all his tests on one day

B) measure how tight the shoes were

C) measure the pressure in the football

D) do his tests on different parts of the field

This is because the variation factors from one day to another may significantly influence the distances the football goes. Among these factors are: the weather and Danny's condition. For example: wind strength, wind direction, any rain influences the skid, etc. Condition example could be: Danny is more tired on one of the days and can't kick as strong.

The other choices do not relate to variability.

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