The hydrostatic head (a measure of water resistance) of fabric treated with 'HydroGuard' is normally distributed with a standard deviation of 450 mm. A quality control check of 25 samples from Production Line X found a mean hydrostatic head of 3200 mm.
Determine a 98% confidence interval for the mean hydrostatic head of fabric from Production Line X.
An independent sample of 30 items from Production Line Y yielded a mean hydrostatic head of 3450 mm. An engineer suggests that the mean resistance of fabric from Line Y is higher than that of Line X.
By clearly stating your hypotheses, test the engineer's suggestion at the 1% level of significance.
The regulatory standard for this fabric is a mean hydrostatic head of μ\muμ mm. When looking at the two production lines individually, at the 1% significance level, there is insufficient evidence to conclude that the mean resistance of Line X is less than μ\muμ, and insufficient evidence to conclude that the mean resistance of Line Y is less than μ\muμ.
Calculate the maximum possible value of μ\muμ, giving your answer to the nearest integer.
355 exam-style questions on OCR (MEI) A Level Maths 2.5 Statistical Hypothesis Testing, covering 2.5.1 Process and language of hypothesis testing, 2.5.2 When to apply 1-tail and 2-tail tests, 2.5.3 Significance level and incorrect rejection, 2.5.4 Null and alternative hypotheses (binomial), 2.5.5 Conduct a binomial hypothesis test, 2.5.6 Critical and acceptance regions (binomial), 2.5.7 Distribution of the sample mean (A-level only), 2.5.8 Hypothesis test for a single mean (A-level only), 2.5.9 Critical and acceptance regions (mean) (A-level only), 2.5.10 Correlation as closeness to a straight line (A-level only), 2.5.11 Inference using a correlation coefficient (A-level only), and 2.5 Statistical Hypothesis Testing. Each one has a worked solution and a mark scheme showing where the marks go.