Use at your own risk, not OraPub's.
-- looper.sql
-- Craig Shallahamer, orapub.craig@gmail.com
-- 4-Apr-2012
-- 
-- Used to help determine if the AWR statistic values
-- are correct at the begin or the end of the snapshot period.
--
set tab off
set linesize 100
col sysstat_lio   format 99999999999
col awr_begin     format a15
col awr_end       format a15
col awr_lio       format 99999999999
col diff_lio      format 999999
col awr_snap_id   format 99999 heading 'AWR|SNAP_ID'
select ss.now, ss.lio sysstat_lio, awr.value awr_lio, ss.lio-awr.value diff_lio, awr.snap_id awr_snap_id, substr(awr.begin_time,11) awr_begin, substr(awr.end_time,11) awr_end
from
  ( 
    select to_char(sysdate,'HH24:MI:SS') now, value lio from v$sysstat where name='session logical reads'
  ) ss,
  (
    select sns.snap_id,
           begin_interval_time begin_time,
           end_interval_time end_time,
           value
    from   dba_hist_snapshot sns,
           dba_hist_sysstat sys
    where  sns.snap_id         = sys.snap_id
      and  sns.dbid            = sys.dbid
      and  sns.instance_number = sys.instance_number
      and  stat_name           = 'session logical reads'
      and  sns.snap_id = (select max(snap_id) from dba_hist_snapshot)
  ) awr
/