To solve this problem, we make use of the z statistic. The formula for z score is:
z = (x – μ) / s
where,
x = is the sample score = 21 or higher
μ = the population mean = 20.8
s = the standard deviation = 4.8
Solving for the z score:
z = (21 – 20.8) / 4.8
z = 0.0417
Next step to do is to find for the p value using the standard distribution tables at z = 0.04. Since we are looking for the probability of getting 21 or higher, therefore this is a right tailed test, hence
p = 0.516
So there is about 51.6% that a student will get a score of 21 or greater.
