Question

The lifespan of an X-ray tube used as part of an X-ray imaging machine follows a normal distribution with a mean of 7 years and a standard deviation of 1.65 years. Standard Normal Distribution Table a. Calculate the probability that a randomly-selected X-ray tube will have a lifespan of: (i) Less than 4 years P(X< 4) = 0 (ii) Greater than 9 years P(X > 9) = 0 (iii) Between 5 and 8 years P(5< X < 8) = 0 b. What length warranty should be established on the X-ray tube so that no more than 3.5% of the units will need to be replaced under warranty? x = 0.00 years Round to two decimal places

Answer 1

DATE Page 2 b] PCX <xt) = 0.035) find inverse - foe Z00352 probability PC Xaul < x-7) = 0.025 1.65 / lie PC z < x-col7) 0.033 1.65 / x-and 7 - 1.8119 1.65 X-7 = 1.8119*) 65 X-7=2.gg x=7+2.99 [x = g.gg years