Exercise 1: Matching Method to Sub-Question — Possible Solution
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The two sub-questions genuinely ask for different kinds of evidence,
even though they're both about the same underlying feature.

"WHAT PERCENTAGE of our users are unhappy" is a quantitative question.
It asks for a measurable proportion across a defined population,
which requires a structured instrument (e.g. a survey with a rating
scale) applied to a large enough sample that the resulting percentage
is genuinely representative. A handful of in-depth interviews couldn't
answer this reliably - a small qualitative sample has no claim to
represent the full user base's own overall proportion.

"WHY the unhappy users feel that way" is a qualitative question. A
percentage alone can't explain the reasoning, emotions, or specific
frustrations behind a negative rating - that requires open-ended
methods (interviews, open-text survey responses, focus groups) that
let unhappy users explain their own experience in their own words,
which a closed-ended numeric scale can't capture.

Together, this is a natural mixed-methods situation: the quantitative
survey establishes the real scale of the problem (how many people, how
serious), while qualitative follow-up (even a smaller number of
in-depth interviews with unhappy users specifically) explains the
mechanism behind it - directly mirroring the chapter's own description
of how mixed methods combines the two.

ANSWER: "What percentage" is a quantitative question, best answered by
a structured survey applied to a large, representative sample. "Why
they feel that way" is a qualitative question, best answered by
open-ended interviews or free-text responses that let users explain
their own reasoning. Using both together - quantitative to measure
scale, qualitative to explain cause - matches the chapter's own
description of a genuine mixed-methods approach.

WHY THIS WORKS AS AN ANSWER
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This matches each sub-question to the correct method type using the
chapter's own stated distinction, and explains specifically why the
other method type couldn't answer that particular sub-question.