A student will measure and record the growth (in height) of two flowering plants every other day for 20 days. Each plant will receive 200mL of water each day, but only one plant will receive 10mL of fertilizer. What is being tested? Do flowering plants grow better with salt water? Does fertilizer help a plant grow taller? How tall do these flowering plants grow? How much fertilizer do flowering plants need?

Every experiment begins with an observation, which then leads to a scientific question that can be tested. In this question, a student measures and records the growth (in height) of two flowering plants every other day for 20 days. He then waters each flowering plants with same amount of water (200mL) but adds 10mL fertilizer to only one group of flowering plant.

This experimental set up implies that fertilizer is the independent variable or manipulated variable of the experiment while the dependent/measured variable is the growth (height) of plants.

N.B: 200mL of water is a constant or controlled variable

Hence, based on the identification of the independent and dependent variables, it can be said that the student is testing IF fertilizer will improve the growth in height of the flowering plants, hence, the scientific question will be: DOES FERTILIZER HELP A PLANT GROW TALLER?