When scientists study data, or information they collect in an experiment, they look for relationships between sets of numbers. For example, in the plant study shown above, the results indicate the taller the plant grows, the more leaves it has. A study of metals may show that the more a metal rod is heated, the longer it becomes. You noticed that the more pages a textbook has, the more it weighs. These are qualitative statements. They describe relationships in words.
When numbers are used to describe the results of an experiment, the statement is quantitative. You can remember the difference between the two kinds of statements if you rememebr that a quantity refers to a number or an amount. Try telling the difference between qualitative and quantitative data in the exercise below.