How do you avoid duplicates when using the randbetween function?

[Monica]

I am trying to use the rand or randbetween function to select random samples,
but I keep receiving duplicate numbers. For example, I have a list of 70
samples but only want to select 25. I type in the formula and then drag it
down 25 cells, but some of those cells have the same number. How do I make
them unique?

Thanks!

 

[daddylonglegs]

If you put the formula

=RAND() in A1 and copy down to A70 then in B1

=RANK(A1,A$1:A$70)

and copy down to B25 this should give you 25 different integers between
1 and 70

 

[JE McGimpsey]

Take a look here:

http://www.mcgimpsey.com/excel/udfs/samplenoreplace.html