Question taken from S1 jan 2008 AQA.
Q)1)b) Sawmill requires batch of logs such that there is a probability of 0.025 that any given log will have a length less than 3.1. determine the value of mu/mean. We also know that the SD is 0.16.
When i look up the Z value for 0.025 i get 1.96. However on the mark scheme when its subbed into the equation it gives
z = 3.1-μ/0.16 = -1.96
i dont understand why it becomes negative? does anyone have an answer to why??