You need to calculate the median from the combined group, you can't do it from the medians and sizes of the groups.
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[TD="align: right"]10[/TD]
[TD="align: center"]2[/TD]
[TD="align: right"]2[/TD]
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[TD="align: right"]10[/TD]
[TD="align: center"]3[/TD]
[TD="align: right"]3[/TD]
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[TD="align: right"]10[/TD]
[TD="align: center"]4[/TD]
[TD="align: right"]4[/TD]
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[TD="align: right"]11[/TD]
[TD="align: center"]5[/TD]
[TD="align: right"]5[/TD]
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[TD="align: right"]12[/TD]
[TD="align: center"]6[/TD]
[TD="align: right"]6[/TD]
[TD="align: right"][/TD]
[TD="align: right"]12[/TD]
[TD="align: center"]7[/TD]
[TD="align: right"]7[/TD]
[TD="align: right"][/TD]
[TD="align: right"]12[/TD]
[TD="align: center"]8[/TD]
[TD="align: right"][/TD]
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[TD="align: center"]9[/TD]
[TD="align: right"]4[/TD]
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[TD="align: right"]11[/TD]
[TD="align: center"]10[/TD]
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[TD="align: right"]8.5[/TD]
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<thead>[TR="bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]
[TH="width: 10px, bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]A9[/TH]
[TH="width: 10px, bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]C9[/TH]
[TH="width: 10px, bgcolor: [URL=https://www.mrexcel.com/forum/usertag.php?do=list&action=hash&hash=DAE7F5]#DAE7F5[/URL] "]B10[/TH]