WST03Topic 3.33 questions
Unbiased estimators, the Central Limit Theorem, confidence intervals and tests for means.
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Original practice questions written in the style of the exam.
The times, minutes, taken by a random sample of 40 students to finish a puzzle are summarised by
(a) Find unbiased estimates of the mean and variance of the times.
(b) Find an approximate 95% confidence interval for the mean time, giving the limits to 2 decimal places.
A random sample of 50 batteries of brand A had mean lifetime hours and unbiased variance estimate . A random sample of 60 batteries of brand B had mean lifetime hours and unbiased variance estimate .
Test, at the 5% level of significance, whether brand A batteries last longer on average than brand B batteries. State your hypotheses clearly.