diff --git a/sp_PressureDetector/sp_PressureDetector.sql b/sp_PressureDetector/sp_PressureDetector.sql
index 6057b7f..720007a 100644
--- a/sp_PressureDetector/sp_PressureDetector.sql
+++ b/sp_PressureDetector/sp_PressureDetector.sql
@@ -769,7 +769,7 @@ OPTION(MAXDOP 1, RECOMPILE);',
                         (w2.hours_wait_time - w.hours_wait_time) / 1000.
                     ),
                 avg_ms_per_wait =
-                    (w2.avg_ms_per_wait - w.avg_ms_per_wait),
+                    (w2.avg_ms_per_wait + w.avg_ms_per_wait) / 2,
                 percent_signal_waits =
                     CONVERT
                     (
@@ -902,7 +902,12 @@ OPTION(MAXDOP 1, RECOMPILE);',
                 CONVERT
                 (
                     decimal(38, 2),
-                    vfs.io_stall_read_ms / (1.0 * vfs.num_of_reads)
+                    ISNULL
+                    (
+                        vfs.io_stall_read_ms / 
+                          (1.0 * NULLIF(vfs.num_of_reads, 0)), 
+                        0
+                    )
                 ),
             total_gb_written =
                 CASE
@@ -920,7 +925,12 @@ OPTION(MAXDOP 1, RECOMPILE);',
                 CONVERT
                 (
                     decimal(38, 2),
-                    vfs.io_stall_write_ms / (1.0 * vfs.num_of_writes)
+                    ISNULL
+                    (
+                        vfs.io_stall_write_ms / 
+                          (1.0 * NULLIF(vfs.num_of_writes, 0)), 
+                        0
+                    )
                 ),
             sample_time = 
                 GETDATE()
@@ -939,8 +949,11 @@ OPTION(MAXDOP 1, RECOMPILE);',
           AND vfs.database_id = f.database_id'
         END +
         N'
-        WHERE vfs.num_of_reads > 0
-        AND   vfs.num_of_writes > 0;'
+        WHERE 
+        (
+             vfs.num_of_reads > 0
+          OR vfs.num_of_writes > 0
+        );'
         );
       
         IF @debug = 1