# Thread: Probability distribution

1. ## Probability distribution

The marks of history in a test are normally distributed with a mean of 55 and a standard deviation of 8 .
( a ) if 10.2 % of the students failed History , find the minimum marks needed to pass

( b ) If 73.4% of the students scored a credit in History , find the minimum marks to score a credit

2. Originally Posted by mathaddict
The marks of history in a test are normally distributed with a mean of 55 and a standard deviation of 8 .
( a ) if 10.2 % of the students failed History , find the minimum marks needed to pass
Let X be the variable and let Z be the normalised variable, such that $Z = \frac{X-55}{8}$ at let W be the pass mark, so you know that $P(X now you must reference your stats table (or use technology) to find the Z value corresponding to 0.102 and solve for W.

Bobak

3. thanks Bobak