Global Journal of Science Frontier Research, F: Mathematics and Decision Science, Volume 21 Issue 4

Where 1 = � { ( ) { ( ) � � − 2 −1 � , 2 = � { ( ) { ( ) � � − 2 −1 � , 3 = � 2{ ( ) { ( ) � � − 2 −1 � � � � ≅ { ( )} −2 8 �1 − 2 � 2 �� 1 − 1 ′ � �� − � 2 − 2 � − ��1 − 2 � + � { ( ) { ( ) � � − ��1 − 2 �� + � 1 − 1 � � − � �� − � + 2 � − � − 2 � − ��1 − 2 � + � { ( ) { ( ) � � − ��1 − 2 �� + � 1 ′ − 1 � � − � � � − � − 2 �1 − 2 �� + � { ( ) { ( ) � � − ��1 − 2 �� � � � ≅ { ( )} −2 4 �� 1 − 1 � − � 1 ′ − 1 � 2 − � 1 − 1 ′ � 2 + 2 −2 �1− 2 � � (23) iii) Baig, Masood and Tarray (2019) suggested an improved class of difference-type estimators for population median under two phase sampling with two auxiliary variables � = � � + 1 � � ′ − � �� � 2 � − � ′ + � ′ � + (1 − 2 ) � � ′ − + � ′ �� where 1 and 2 are unknown constant. � � � = 1 4 � 1 − 1 � � 1 2 − 2 � Where 1( ) = and 2( ) = 1 2 + Towards the Efficiency of the Ratio Estimator for Population Median in Survey Sampling 1 Global Journal of Science Frontier Research Volume XXI Issue IV Year 2021 45 ( F ) © 2021 Global Journals Version I N otes