Question 1

Why use p = 0.5 when unsure?

Accepted Answer

It maximizes required sample size, providing conservative planning when true proportion is unknown.

Question 2

Does response rate affect this n?

Accepted Answer

Yes — if only 20% respond, send invitations to n ÷ 0.20 to achieve target completes.

Question 3

Is normal approximation always valid?

Accepted Answer

Require np and n(1−p) ≥ 5 typically. Small samples need exact binomial methods.

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