The time a laser printer takes to print a picture is found t

The time a laser printer takes to print a picture is found to be variable, depending on a number of different aspects of the picture such as size, precision, type of computer file, and so on. Over a few weeks the time taken to print each picture on a particular laser printer is recorded and found to have a mean time of 87 seconds and a standard deviation of 23 seconds.
(a) Let Y be the total time taken to print seven different pictures selected at random. What are the mean and standard deviation of Y? [2 marks]
(b) Let W be the total time taken to print seven copies of the same randomly selected picture. Assuming the times taken to print each copy of the same picture are identical, what are the mean and standard devia-tion of W? [2 marks]

(a),(b) ask total time and (a)\'s sample is \"seven different pictures selected at random\"

(b)\'s sample is \"seven copies of the same randomly selected picture\"

Solution

a)

mean = 87

SD = 23 / sqrt 7 = 8.69

b)

for the other literals

I can gladly help you but you should post it in a new question