X and Y are independent normal variables for the time for two consecutive process steps: X has mean 12 min and standard deviation 1.5 min, Y has mean 20 min and standard deviation 2 min. Find the standard deviation σ of X + Y.
Drag z so that the shaded area under the standard normal curve, to the left of z, is 0.0951. Find z to two decimals.
X is normal with mean 12 min and standard deviation 1.5 min; Y is independent and normal with mean 20 min and standard deviation 2 min. Find the probability P that X + Y is more than 35.1 min. Round z to two decimals.
The bag weights are normally distributed with mean 250 g and standard deviation 5 g. What fraction lies between 242.5 and 259.25 g? Give P as a decimal.
The bag weights are normally distributed with mean 250 g and standard deviation 5 g. Find the value x below which 90% of them lie (the 90th percentile).
The delivery times are normally distributed with mean 32 min and standard deviation 6 min. Find the value x below which 5% of them lie (the 5th percentile).
Full step-by-step solutions: practise this topic on examproblems.com.