Median & Range Charts Statistical Process Control • Alfaro Rodea Jonathan • Guerrero Díaz Florencia • Hernández Miranda José Carl • López alas José An!el • "eláz#uez A$eleira %stefanía &'("%R(DAD A&)*'*MA D%L %)AD* D% M*R%L*F AC&L ) AD D% C(%'C(A+&(M(CAe ('G%'(%R(A
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• A statistical tool used to distin!uish .et/ee$ariation resultin! fro0 co00on causes andresultin! fro0 special causes1 ho/in! in a proceor insta.ilit2 o$er ti0e1
are ordered fro0 lo/ to hi!h 6 or $ice $ersa7 1 (n the$ent that the sa0ple size is a e$en nu0.er of dat5 the 0edian is the a$era!e of the t/o 0iddl$alues 8 and /hen the sa0ple size is an odnu0.er of data5 the 0edian is the central $alue1
)he 0edian has ad$anta!es as a 0eancontrollin! the position for those cases /herecontrolled population is not nor0al and presestron! as200etr21 Also has an ad$anta!e in eause1
)his 0eans that the 0edian lea$es the sanu0.er of $alues .elo/ than a.o$e5 does re#uire perfor0in! an2 calculation for o.tainin! as0all sa0ple sizes 6as are usuall27 is o.tained
inspection of the sa0ple 9 for e3a0ple in a sa0size of <$e ti0es the 0edian is the third $alu.oth !oin! fro0 lo/ to hi!h and hi!h to lo/1
%3a0ple9et data pair9
=5>5?5@55B55=5?55>5
Data are ordered fro0lo/est to hi!hest9=5 =5 >5 >5 ?5 ?5 5 5 5 B@
)he 0edian is9?1
%3a0ple9*dd data set9
=5>5?555B55=5?
Data are ordered fro0lo/est to hi!hest9=5 =5 >5 ?5 ?5 5 5 B5
A hotel 0easures custo0ersatisfaction /ith a sur$e2 thatrecords a ratin! fro0 I 6/orst#ualit27 to I 6.est #ualit271 %$er2/eeK the hotel calculates a$era!eratin!s for the /eeK1
)he 0ana!er desires to Kno/ if#ualit2 is consistent or chan!in!
o$er ti0e1 ,eeKl2 ratin!s for aseries of /eeKs are 15 1I5 1@5@1=5 1=5 15 1B5 @15 1=5 15and B11 )he 0ana!er isconcerned a.out the last /eeKsratin! of B11 Does it represent astatistical ano0al25 or is it si0pl2 aresult of rando0 $ariation-1
o5 one thin! 0ana!er 0a2 /ant Kno/ is if that B1 <ts rando0 pattern of other data5 or if it donot1