The viscosity of a specific liquid polymer, VVV, is known to be normally distributed with a mean of 1420 mPa·s and a standard deviation of 115 mPa·s. A quality control engineer takes a random sample of 24 independent batches to monitor the stability of the production line. Determine the probability that the mean viscosity of this sample, Vˉ\bar{V}Vˉ, is less than 1385 mPa·s.
390 exam-style questions on AQA A Level Maths 2.4 N: Statistical distributions, covering 2.4.1 Discrete distributions and the binomial, 2.4.2 The Normal distribution (A-level only), and 2.4.3 Selecting an appropriate distribution (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.