Suppose the number of defects in a sweater from a population of sweaters produced from a textile factory are normally distributed with an unknown population mean and a population standard deviation of 0.06 defects. A random sample of sweaters from the population produces a sample mean of x¯=1.3 defects. What value of z should be used to calculate a confidence interval with a 95% confidence level? z0.10 z0.05 z0.025 z0.01 z0.005 1.282 1.645 1.960 2.326 2.576

The standard deviation of the daily demand for a product is an important factor for inventory control for the product. Suppose that a pharmacy wants to estimate the standard deviation of the daily demand for a certain antibiotic. It is known that the daily demand for this antibiotic follows an approximately normal distribution. A random sample of 25 days has a sample mean of 121 orders for this antibiotic with a standard deviation of 10.3 orders. Find a 99% confidence interval for the population standard deviation of the daily demand for this antibiotic. Then give its lower limit and upper limit. Carry your intermediate computations to at least three decimal places. Round your answers to at least two decimal places. (If necessary, consult a list of formulas.) Lower limit: Upper limit: X 3

Find an 80% confidence interval for the heart rates of US adults over 25 if a sample of size 15 is SAR from the male population. The sample yields an average rate of 69.9 beats per minute. The standard deviations for the samples is 3.5 beats per minute. Assume heart rates in humans are normally distributed.