Classify the variable as nominal-level, ordinal-level, interval-level, or ratio-level measurement.
Blood types - O, A, B, AB
Interval
Ratio
Ordinal
Nominal

Blood types, such as O, A, B, and AB, are classified as nominal-level measurements. This means they are categorical variables that label different groups without any inherent order or ranking among them. Think of it like a fun party where each blood type is a different guest; they all play unique roles but none is superior to the other!

When collecting blood type data, it’s essential to remember that while the labels are distinct, they don’t measure quantity or carry a specific rank. A common mistake is treating nominal data as having a meaningful order, like putting them in a ranking system. Keep it simple; each type is valuable on its own!