Arrange the numbers smallest to largest:

#1  = 1.9
#2  = 2.0
#3  = 2.1
#4  = 2.9
#5  = 3.1
#6  = 3.4
#7  = 4.7
#8  = 5.0
#9  = 5.4
#10 = 6.8

There are 10 numbers in the list

To find , which is called "the 25th percentile",
or "the 1st quartile"

Multiply  by , getting 

Since that is not a whole number, we round up to 3.

So data value #3 is .

So ,

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To find , which is called "the median", "the
50th percentile", or "the 2nd quartile"

 Multiply  by , getting 

Since that is a whole number, we find the ordinary
average of data values #5 and #6:

So ,

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To find , which is called "the
75th percentile", or "the 3rd quartile"

Multiply  by , getting 

Since that is not a whole number, we round up to 8.

So data value #8 is .

So 

Edwin