How do I pull out every nth value from a column of data in excel?

[m.mines]

I have two sets of data: one which has information every hour, and another
with information every 15 min. I want to down-size the data that has infm
every 15 min so that I can look at it on the hourly scale and compare to the
other data set. The data set is too large to manually delete the extra rows.
I'm using Excel 2003.

[Dav]

with out seeing your data the easiest way is probably to create a helper column eg calcuating the minutes of the times perhaps minute(b1), or using a left right or mid function if the time is text eg right(b1,2)

Then copy the formula down to the bottom of your data, select your data, then sort by this column and then delete the rows you do not want as a block, rather than individually.

Regards

Dav