Question

Force data taken over a long term from a bridge support strut shows the average force on the strut to be 428.5 lbf with a standard deviation of 10.5 lbf. To ensure longevity of the strut, the loading needs to always stay below 475 lbf. What percentage of the time is the force loading below this maximum value? (Use Excel to calculate your answer and give the Excel formula used.)

Answer 1

Solution:-

Mean = 428, S.D = 10.5

The percentage of the time is the force loading below this maximum value is 0.9999

x = 475

By applying normal distribution:-

$z = \frac{x-\mu }{\sigma }$

z = 4.4286

P(z < 4.4286) = 0.9999