Your Practice Set – Applications and Interpretation for IBDP Mathematics
71
Paper 1 – Standard Deviations
Example
The height of an orchid , in centimetres , from a store is studied . A random sample of 20 orchids is measured . It is given that the 95 % confidence interval for the population mean is ( 21.75 , 22.35 ) .
( a ) Find an unbiased estimate of the population mean .
Let
2
� be the known population variance .
( b ) Find � .
[ 2 ]
[ 3 ]
Solution
( a ) An unbiased estimate � X
( A1 ) for correct approach
21.75 � 22.35 �
2 � 22.05 cm
A1
� � � ( b ) 22.35 �21.75 �2 ( 1.959963986 ) � �
� 20 �
� � 0.6845231831cm
M1A1
� � 0.685 cm A1
[ 2 ]
[ 3 ]
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