QUESTION A4 (5 marks) The owner of a metal stamping factory wants to estimate the mean weight of his metal parts to an accuracy of 10.5 grams and with a confidence level of 95%. Given that the population standard deviation of the metal parts is 4 grams. Estimate the appropriate sample size to use. QUESTION A5 (5 marks) From a random sample of 250 diabetics, it was found that 110 of them were women. Construct a 90% confidence interval for the true proportion of woman diabetics. QUESTION A6 (5 marks) The average life-span of ten LED light bulbs is 900 hours with standard deviation of 50 hours. Find a 99% confidence interval for the population mean life-span, assuming that the life-span of the light bulbs is normally distributed