Question

a drinks machine dispenses coffee into cups. A sign on the machine indicates that each cup contains 50 ml of coffee. the machine actually dispenses a mean amount of 55ml per cup and 10% of the cups contain less than the amount stated on the sign. assuming that the amount of coffee dispensed into each cup is normally distributed find the standard deviation of the amount of coffee dispensed per cup in ml.

Answer 1

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http://davidmlane.com/hyperstat/z_table.html

Answer 2

a drinks machine dispenses coffee into cups. a sign on the machine indicates that each cup contains 50 ml of coffee. the machine actually dispenses a mean amount of 55 ml per cup and 10% of the cup contain less than the amount stated on the sign. assuming that the amount of coffee dispensed into each cup is normally distributed, find (i) the standard deviation of the amount of coffee dispensed per cup in ml. (ii) the percentage of cups that contain more than 51 ml. following complaints, the owners of the machine made adjustments. only 2.5 % of the cups now contain less than 50 ml. the standard deviation of the amount dispensed is reduced to 3 ml. assuming that the amount of coffee dispensed is still normally distributed, (iii) find the new mean amount of coffee per cup. answers