How can we find the mean 
of the weight of a population of students which is found to be normally distributed with standard deviation 2 Kg and the 30% of the students weigh at least 53 Kg.
Let the random variable W denote the weight of the students, so that
)
We know that=0.3)
Since we don’t know the mean, we cannot use the inverse normal. Therefore we have to transform the random variable
to that of
)
, using the transformation 
we have the following
=0.3%20\Rightarrow%20P(\frac{X-%20\mu}{\sigma}%20\geq%20\frac{53-%20\mu}{2})=0.3)
=0.3)
Using GDC Casio fx-9860G SD
MAIN MENU > STAT>DIST(F5)>NORM(F1)>InvN>
Setting Tail: right
Area: 0.1
:1
:0
We find that the standardized value is 0.5244
Therefore
)
of the weight of a population of students which is found to be normally distributed with standard deviation 2 Kg and the 30% of the students weigh at least 53 Kg.
The answer is from www.ibmaths4u.com
We know that
Since we don’t know the mean, we cannot use the inverse normal. Therefore we have to transform the random variable
we have the following
Using GDC Casio fx-9860G SD
MAIN MENU > STAT>DIST(F5)>NORM(F1)>InvN>
Setting Tail: right
Area: 0.1
We find that the standardized value is 0.5244
Therefore
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