Transcript: People make many statements in everyday life. Some statements are quantitative and some are qualitative. You might say, “This piece of music is great,” or, “It was cold outside yesterday.” The first statement cannot be quantified. It may be true for you and not true for one of your friends. It’s a purely qualitative statement. The second statement can be quantified, but we need a system of units. Scientists only deal with quantitative statements. Every statement about science that involves a measurement has two parts. It has a quantity and a unit, and science always deals with these two things coupled together. So when I say, “It was cold yesterday,” I need a system of units and a measurement. And even if I say, “Fifteen degrees,” I have to tell you which measurement system I was using, Celsius or Fahrenheit. If I said, “The Dow fell fifty points yesterday,” that’s a quantitative statement, but you would have to know something about the units; which means you would have to know something about what goes into making a point on the Dow-Jones Industrial Average. So in general scientists always deal with quantitative measurements, and those measurements must have units attached.