The other day, I noticed that the Peet's Coffee near me added a footnote to their menu sign.
I'm talking about this note at the bottom:
Milk-based beverage calories calculated using 2% milk, except for Havana Cappuccino and Black Tie.... 2,000 calories a day is used for general nutrition advice, but calorie needs vary...
These few sentences really speak to why an analyst must know how metrics are defined before he or she can interpret them.
What I learned about measurement from this calorie estimation footnote:
- The number of calories for the same beverage depends on assumptions, such as whether one is using 2% milk, or no-fat milk, or whole milk
- Definitions have exceptions: here, Havana Cappuccino and Black Tie are exceptions - they didn't say in what way but I know those two drinks use condensed milk
- There may be other hidden assumptions
- The calorie metric only attains meaning when a reference level (daily calorie need) is provided
- The reference level is provided as a one-size-fits-all number; even the writer of this note realizes is too generalized
- The reference level is defined with another pile of hidden assumptions
- I wonder if the calorie counts come from formulas or some kind of lab measurement
Whether one believes the calorie estimation on restaurant menus depends on whether one knows the assumptions used to produce those estimates. Also, trusting a metric is just one step; one must then figure out how to use the metric for a purpose.