Quantitative and qualitative data

The two data types

Quantitative data — data in numbers.

• How many students would buy; what percentage prefer each option; average spend; how often people buy.
• Answers how many, how much, how often.

Qualitative data — data in words, describing opinions, reasons and feelings.

• Why people prefer one option; what puts them off; how they describe the product.
• Answers why and what does it mean to them.

	Quantitative	Qualitative
Form	Numbers, counts, percentages	Words, quotes, descriptions
Collected by	Closed questions, sales records, observation counts	Open questions, interviews, focus groups
Strength	Countable, comparable, can be graphed; larger samples possible	Explains reasons; reveals things you did not think to ask
Weakness	Tells you what, not why; a badly framed option distorts everything	Hard to count and compare; small samples; researcher interpretation
Best used for	Establishing the size of a response	Establishing the reason behind it

Question types produce data types

• Closed questions produce quantitative data: yes/no, multiple choice, rating scales, ranked lists.
• Open questions produce qualitative data: "What would stop you buying this?"
• A good questionnaire uses mostly closed questions — so the results can be counted — with one or two open questions at the end to catch reasons you did not anticipate.

Writing questions that work

• One idea per question. "Is the product tasty and good value?" cannot be answered by someone who thinks it is tasty and expensive.
• No leading questions. "Don't you agree that $4 is a fair price?" tells the respondent the answer you want.
• Offer balanced options. A scale running from "good" to "excellent" cannot record a negative view.
• Use plain words, and define anything ambiguous — "often" means different things to different people, so ask "how many times per week".
• Include a genuine opt-out. Without "I would not buy it at any price", everyone is forced into a purchase they may not make.
• Keep it short. Every extra question costs you responses.

Recording the data

• Decide before you collect how you will record the answers — a spreadsheet with one row per respondent and one column per question is the simplest structure and it makes graphing straightforward.
• Record qualitative answers verbatim. A quote is evidence; a paraphrase written from memory is not.
• Keep the raw data. Assessors expect to see it, and it is what allows you to check a surprising result rather than guessing at it.