Question

A normal distribution has a mean of 98 and a standard deviation of 6. What is the probability that a randomly selected x-value from the distribution is at least 80?

Answer 1

Normalize 80 as
(80-98)/6=-3
Look up the probability from a normal distribution table for -3 to ∞.
(It is the same value from -∞ to +3, depending on the availability of the table).
I get 0.9987.