Final answer:
A variable's measurement level is determined based on its properties, including how it can be categorized, ordered, and whether it has a true zero point. The four levels are Nominal, Ordinal, Interval, and Ratio. Selecting units of measurement requires consideration of the object's size and the practicality of the measurement unit.
Step-by-step explanation:
To determine a variable's measurement level, consider what the data represents and the properties it possesses. Measurement levels, from the lowest to the highest, include Nominal, Ordinal, Interval, and Ratio. The Nominal scale level is for categorical data that cannot be ordered nor used in calculations, such as colors or yes/no responses. For example, sorting crayon colors lacks inherent order, thus is nominal. The Ordinal scale level involves ordered data, but the differences between data points cannot be measured, like ranking athletic ability as superior, average, or above average. The Interval scale level data has a definite order with measurable differences, but no true zero point, such as temperature measured in Celsius or Fahrenheit. Lastly, the Ratio scale level data is ordered, with measurable differences and a true zero point, allowing for ratios to compare, for instance, the lengths of a street or the size of a worm.
When selecting units of measurement, choose those that match the scale of what is being measured. For large distances, such as between towns, use kilometers or miles. For smaller objects, like a light switch height or refrigerator width, inches or centimeters would be appropriate. Understanding and selecting the right metric or customary units of measurement involves comparing their relative sizes and practical applications to the object at hand.