Why is it important to control variables in an investigation?

science question...little confuzzlingx[[Why is it important to control variables in an investigation?
Lets say you want to know if your dog is affected by whether the sun is shiny or if its cloudy. Now there are many things that could change his mood, it could be the food, or the way you dress. So if you are testing his mood for two days, one day its shiny and one day its cloudy, it is important that you kept the other factors that affect his mood under ';control'; and unchanged, otherwise you won't know if his mood changed because of the sun shine or something elseWhy is it important to control variables in an investigation?
You must only change one variable at a time whilst investigating a phenomenon. This is because if you change more than one, it is not possible to tell which variable was responsible for any observed effect.





Hence, ideally you will have fully control over all variables.