In one year, in one school, thirteen children passed the eleven
plus. So the head teacher, the teachers, the governors and the parents all voted
for the teacher to be offered promotion. The next year, with a different
teacher, only five children passed. Assuming that an equal number of children
in the school sat the examination, do the new figures suggest that the head, the
teachers, the governors and the parents were all wrong? Is the reduction in the
number of eleven plus passes down to chance?
One of the parents, in Year One, is a statistician and is
co-opted to look into the potential problem. After all no one wants the same
thing to happen.
X, the smaller number of children who passed = 5
Y, the number who passed in the previous year = 13
N = x + y
= 5 + 13
= 18
Because the number does not exceed forty the statistician
looks at what is called the 50% Probability Test. This shows that if x = 5 and
y = 13 – with a total of 18 then there is a probability of 10%.
The difference between the two eleven plus pass rates is not
statistically proven.
The head can relax.
The teacher keeps the job.
The governors can be proud of their school.
The parents can maintain their support.
The children can rest easy. (Not that they worried much
anyway!)
