What are the components needed in order for an experiment to be valid? identify these components in the following experiment: a scientist is testing a new plant food to see if it causes plants to grow faster. the scientist tests two plants with the new plant food, and two plants he grows without plant food.

He is missing a (real) control. Growing two plants without plant food at all doesn't count; in order to see if the new food is better, he must also grow plants with the original food in order to compare it. 

He does have an independent variable. This is the type of plant food. It's independent because he has direct control over it.

He needs to give plants the same conditions besides food: same water (amount), same light exposure, same temperature, etc.

He needs to choose a quantitative way to measure how much the plants grew, like mass or length.