In Problems 11–13, classify the variable as qualitative or quantitative. If the variable is quantitative, state whether it is discrete or continuous.
12. Weight in carats of an uncut diamond
Step 1 of 5) A letter grade is a variable measured at the ordinal level because the values of the variable can be ranked, but differences in values have no meaning. For example, an A is better than a B, but A - B has no meaning. When classifying variables according to their level of measurement, it is extremely important that we recognize what the variable is intended to measure. For example, suppose we want to know whether cars with 4-cylinder engines get better gas mileage than cars with 6-cylinder engines. Here, engine size represents a category of data and so the variable is nominal. On the other hand, if we want to know the average number of cylinders in cars in the United States, the variable is classified as a ratio (an 8-cylinder engine has twice as many cylinders as a 4-cylinder engine).