Apps. and Interpretation for IBDP Maths Ebook 1 | Page 310

Your Practice Set – Applications and Interpretation for IBDP Mathematics
Exercise 88
1. A random variable X is normally distributed with � � 240 and � � 15.
(a) Find the lower quartile of X .
(b) Find the upper quartile of X .
(c) Hence, find the interquartile range of X .
[2]
[2]
[2]
2. A random variable X is normally distributed with � � 160 and � � 8.
(a) Find the value of the 30th percentile of X .
(b) Find the value of the 70th percentile of X .
(c) Hence, find the difference between the 70th percentile and the 30th percentile.
[2]
[2]
[2]
3. A random variable X is normally distributed with � � 88 and � � 4 . Find the difference
between the 90th percentile and the 10th percentile.
4. A random variable X is normally distributed with � � 50 and � � 3. The values s and
t , where s� t, are the data values that divide the whole distribution into 3 equal parts.
Find t� s.
[6]
[6]
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