10.2 Matched Pairs

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CONSUMER ADVOCATES GROUP ASKED ANALYSIS TO CONDUCT A STUDY OF HOW TIME POPULATION AVERAGE CAR MAINTENANCE CHANGED AFTER SIGNING FOR THE SPECIAL DISCOUNT PROGRAM RECORDS WERE OBTAINED FROM THE SAME 16 DRIVERS ON THEIR EXPENSES FOR TWO CONSECUTIVE YEARS INDIVIDUAL DIFFERENCES , ( YEAR 2016 ) - ( YEAR 2015 ) , WERE ASSUMED TO BE NORMALLY DISTRIBUTED WITH UNKNOWN PARAMETERS . SAMPLE SUMMARIES DERIVED FROM SELECTED DRIVERS ( MEASURED IN DOLLARS PER YEAR ) ARE SHOWN BELOW ( X- BAR ) = (YEAR 2015 ) SAMPLE MEAN - 856.90 ( V- BAR ) = ( YEAR 2016 ) SAMPLE MEAN - 741.90 SAMPLE STANDARD DEVIATION FOR INDIVIDUAL DIFFERENCES WAS FOUND AS 250.00B . ESTIMATE THE POPULATION AVERAGE DIFFERENCE ( YEAR 2016 ) - ( YEAR 2015 ) WITH THE 95% CONFIDENCE . PRESENT THE CONFIDENCE LIMITS IN THE FORM ( MID - POINT ) MARGIN OF ERROR ) CRITICAL VALUE ( S ) MID - POINT = MARGIN OF ERROR UPPER CONFIDENCE LIMIT LOWER CONFIDENCE LIMIT