To solve this problem, we make use of the z statistic. What we have to do here is to find for the z score using the given data and from the standard probability tables for z, we locate the proportion of the fish longer than 12 inches.
The formula for calculating the z score is:
z = (x – μ) / σ
where,
x = the sample value = 12 inches
μ = the sample mean = 11 inches
σ = 2 inches
so,
z = (12 – 11) / 2
z = 1 / 2
z = 0.5
Since we are looking for the values greater than 12, so this is a right tailed test. Using the tables, the value of p at this value of z is:
p (z = 0.5) = 0.3085
Therefore there is a 30.85% probability that the fish is longer than 12 inches.
