Q. If at some time in the future a sample of 50 bars are measured, and a mean value is found of 8.12 mm with a standard deviation of 0.14 mm. Test whether this samplehas changed from the original batch to a statistical significance of 95%.

Answer

n=50, μ = 8.12, σ = 0.14,

z = [ μ - x ] / sqrt(n) / σ

how do i get x??