According to one of the Western Electric rules for quality control, a produced item is considered conforming if its measurement falls within three standard deviations from the target value. Suppose process is in control so that expected value of each measurement equals target value. What percent of items will be considered conforming if the distribution of measurements is:
a) normal(μ, σ^2)
b) Uniform(a, b)
For a, I got that we need P(-3σ <= X <= 3σ). I am just not sure how you go about standardizing this and finding percent of conforming items when you have no values for σ and μ and a and b so I am kind of stuck at this point. Would anyone be able to lead me in the right direction here?