A study is discussed the purity of oxygen from a certain supplier. Assume that the mean was 99.61 with a standard deviation of 0.08. Assume that the distribution of purity was normal. Below what purity value would you expect to represent the smallest 25% of the population?

Answer 1

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion and its Z score. Insert the values in the equation above to solve for the score.