1-2 Types of Data 15 analyzing, and interpreting those data; and then drawing conclusions based on them. We now have two different definitions of statistics, but we can determine which of these two definitions applies by considering the context in which the term statistics is used. The following example uses the first meaning of statistics as given on the previous page. Parameter, Statistic EXAMPLE 1 There are 250,342,875 adults in the United States. In a survey of 1659 randomly selected adults, 28% of them said that they own a credit card. 1. Parameter: The population size of 250,342,875 adults is a parameter, because it is the entire population of all adults in the United States. (If we somehow knew the percentage of all 250,342,875 adults who have a credit card, that percentage would also be a parameter.) 2. Statistic: The sample size of 1659 adults is a statistic, because it is based on a sample, not the entire population of all adults in the United States. The value of 28% is another statistic, because it is also based on the sample, not on the entire population. YOUR TURN. Do Exercise 1 “Parameter and Statistic.” Quantitative, Categorical Some data are numbers representing counts or measurements (such as heights of adults), whereas others are attributes (such as eye color of green or brown) that are not counts or measurements. The terms quantitative data and categorical data distinguish between these types. DEFINITIONS Quantitative (or numerical) data consist of numbers representing counts or measurements. Categorical (or qualitative or attribute) data consist of names or labels (not numbers that represent counts or measurements). CAUTION Categorical data are sometimes coded with numbers, with those numbers replacing names. Although such numbers might appear to be quantitative, they are actually categorical data. See the third part of Example 2 that follows. Include Units of Measurement With quantitative data, it is important to use the appropriate units of measurement, such as dollars, hours, feet, or meters. We should carefully observe information given about the units of measurement, such as “all amounts are in thousands of dollars” or “all units are in kilograms.” Ignoring such units of measurement can be very costly. The National Aeronautics and Space Administration (NASA) lost its $125 million Mars Climate Orbiter when the orbiter crashed of ot h Go Figure 7 billion: The world population that was exceeded in early 2012, which is 13 years after it passed 6 billion. m. of cs he Units of Measurement The television news show 60 Minutes reported on the increased risk of cancer from using certain laminate flooring products made in China and sold by Lumber Liquidators. The Centers for Disease Control and Prevention (CDC) stated that the risk of cancer was actually three times higher than had previously been reported. The error occurred because in some of the first calculations, the CDC neglected to convert feet to meters. Lumber Liquidators discontinued sales of the problem laminate flooring.
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