Question

Testing of a given concrete sample has yielded a normal distribution with a mean compressive strength of 3200 psi with a standard deviation of 275 psi. You require a compressive strength of at least 2950 psi.  What is the probability that this concrete meets your needs?

Answer 1

Solution :

Given that ,

mean = = 3200

standard deviation = = 275

P(x 2950 ) = 1 - P(x   2950 )

= 1 - P((x - ) / (2950 3200) / 275)

= 1 -  P(z -0.909 )  

= 1 - 0.1817   

= 0.8183

Probability = 0.8183