I am trying to solve the following problem.
The diameter of a product manufactured can be regarded as a random variable E. During an inspection products with a thickness greater than 1.01 mm or less than 0.99 mm are sorted out. It has been found out that:
P(E > 1.01) = 8%
P(E < 0.99) = 2%
determine the mean and standard deviation.
What i have concluded is the following:
P(0.99 < E < 1.01) = 1 - (0.08 + 0.02) = 0.90
So I suppose that I need to do some reverse lookup in the normal distribution table but what I can see I have two unknown variables, both the mean and the deviation. I think I need some help to proceed.
In your table, what is the length between the 2 values corresponding to these probabilities ? Since in your real case it is 0.02, it tells you how to scale the variable... and thus the standard deviation. From here I guess you will know how to solve the last degree of freedom, right ? :-)