Also having some trouble with this one:

Suppose we assume that the temperatures of healthy humans is approximately normal with a mean of 98.6 degrees and a standard deviation of 0.8 degrees.

(a) If 130 people are selected at random, what is the probability that the average temperature for these people is 98.25 degrees or lower?

(b) Would you consider an average temperature of 98.25 degrees to be an unlikely occurrence, given that the true average temperature of healthy people os 98.6 degrees. Explain

The answers:

(a) ≈0

(b) Yes; the mean value is 98.25, which is almost 5 standard deviations below the assumed mean of 98.6

Any help will be greatly appreciated, as i am interested in how these answers are obtained.