Learn in the textbookClassifying Data by Attribute and Structure
DefinitionQualitative data (質的データ) marks kinds or categories, so adding or averaging it means nothing.
ExplanationIt records which category something falls into, such as blood type, occupation, or a satisfaction level (dissatisfied, neutral, satisfied). Summaries count the cases or shares in each category, and pie charts or 100% stacked bar charts often show the breakdown.
AnalogyThink of splitting a school sports day into red and white teams. Adding "red" to "white" produces nothing; all you can count is how many people are on each team.
Memory hookIn English it is "qualitative," from the same root as "quality": data that answers "what kind."