Question 1124690
z=(x-mean)/sd
z<(16-21.8)/5.2 or <-1.12 for probability 0.1314

z is between (17.8-21.8)/5.2 and (25.8-21.8)/5.2 or between -0.77 and +0.77.  That has probability 0.5587

z>(32.5-21.8)/5.2 or >2.06 for probability 0.0197

The last would be unusual with 2% probability, but in a group of 1000 students 20 would be expected to score this high or higher. Large groups with small probability will have some low probability occurrences.  Smaller groups would be less likely.  One also needs to define what is considered unusual, 5%? 1%?