A manufacturer of high-precision capacitors specifies that the mean capacitance of a specific model is 14.50 μF14.50\, \mu \text{F}14.50μF. A quality control engineer believes that a recent manufacturing fault has resulted in a lower mean capacitance than specified. A random sample of 81 capacitors is tested, yielding a sample mean of 14.38 μF14.38\, \mu \text{F}14.38μF and a standard deviation of 0.45 μF0.45\, \mu \text{F}0.45μF. Test the engineer's belief at the 1% level of significance. State your hypotheses clearly.
616 exam-style questions on Edexcel A Level Maths The Normal Distribution, covering 3.1 The Normal Distribution, 3.2 Finding Probabilities for Normal Distributions, 3.3 The Inverse Normal Distribution Function, 3.4 The Standard Normal Distribution, 3.5 Finding the mean and standard deviation, 3.6 Approximating a Binomial Distribution, and 3.7 Hypothesis Testing with the Normal Distribution. Each one has a worked solution and a mark scheme showing where the marks go.