QCEVault

Statistical inference — Question 284

Original QCE Vault practice · 4 marks

Q284 · Practice questionTechnology-activeSimple familiar4 marks

QUESTION 284 (4 marks)

A random sample of 12 independent tests records the times shown in the table, in minutes. Assume test times in the population are normal. The sample standard deviation is s=1.0445s=1.0445 minutes. Use z=1.96z=1.96 and the QCAA approximate interval x‾±zs/n\overline x\pm zs/\sqrt n.
Question 137 stimulus; see the question for exact data and required construction.
a)
Determine the sample mean.
[1 mark]
b)
Determine an approximate 95% confidence interval for the population mean, to three decimal places.
[2 marks]
c)
A supplier claims the mean test time is 11 minutes. Evaluate whether the sample interval supports the claim.
[1 mark]
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