QCEVault

Statistical inference — Question 234

Original QCE Vault practice · 5 marks

Q234 · Practice questionTechnology-activeComplex familiar5 marks

QUESTION 234 (5 marks)

A 90% mean confidence interval uses z=1.645 and n=64. A new study uses 95% confidence, z=1.96, with the same assumed standard deviation.
a)
Find the least sample size ensuring the new interval is no wider.
[3 marks]
b)
Explain the width change at unchanged sample size and give the width ratio.
[2 marks]
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