The ages of students at a university are normally distributed with a mean of 21. What percentage of the student body is at least 21 years old? a. 50% b. It could be any value, depending on the magnitude of the standard deviation. c. 1.96% d. 21%

50%

Step-by-step explanation:

Recall : When given a normal or Symmetric distribution, the mean of the distribution is at the centre with 0.5 or 50% of the distribution to either side (right and left) of the distribution.

Hence, if the mean = 21 ; then the percentage of student body with atleast 21 years is the percentage to the left of the distribution, which is 50%.

Therefore, P(x ≤ 21) = 0.5 = 50%

d

step-by-step explanation:

in simplified version   it would be x ≤-4

step-by-step explanation:

multiply each term in x ≤-4 by -1