Question 176894
Let's order the data set
2,2,4,5,6,10,12,19,21
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Number of data points, N, is 9.
The lower (first) quartile {{{Q[1]}}} would be the Mth data point in the ordered data set,
{{{M=(N+1)*(25/100)=(9+1)*.25=2.5}}}
Since it's not an integer, we round up to 3 or the third data point. 
{{{Q[1]=4}}}
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Since it's an odd numbered data set, choose the middle value from the ordered data set, that's the median.
{{{M=6}}}