We are given the following values:
μ = 0.40 and σ = 0.09
To find for the probability, we calculate for the z score and then use the standard probability tables to find for the P at calculate z score value.
z = (x – μ) / σ
a. at x > 0.60
z = (0.60 – 0.40) / 0.09
z = 2.22
Using the tables to find for P using right tailed test:
P = 0.0132 = 1.32%
b. at x < 0.30
z = (0.30 – 0.40) / 0.09
z = -1.11
Using the tables to find for P using left tailed test:
P = 0.1335 = 13.35%
c. from the tables, the z score at P = 0.95 is:
z = 1.645
Calculate for x given z:
1.645 = (x – 0.40) / 0.09
x = 0.548
Hence the largest 5% are all greater than 0.548 mg/cm^3