PLEASE help me make this a controlled experiment quick!?

Question

ok my experiment is to take samples of soil from many different places and test them all to see which one has the most amount of led in it..but i need to make it a controlled experiment (testing one variable) and im kind of stuck on making it one

Answer 1

You might rephrase your topic to be:

"Do residential areas have more lead in the soil?"
(Control group: soils a certain distance away from houses. Experimental group: soils closer to houses.)

or "Does street pollution affect the level of soil pollution?"
(Control group: soils a certain distance away from streets.
Experimental group: soils within that distance from streets.)