Check if is number on AVG function by case statement

$req = $db->prepare('SELECT AVG(CASE target WHEN ("NPS" OR "NA") THEN target ELSE NULL end) AS target, AVG(CASE planned_qty WHEN ("NA" OR "NPS") THEN null ELSE planned_qty end) AS planned_qty, AVG(CASE encap_planned WHEN ("NA" OR "NPS") THEN null ELSE encap_planned end) AS encap_planned,AVG(CASE open_wo WHEN ("NA" OR "NPS") THEN null ELSE open_wo end) AS open_wo  WHERE date_production >= CAST("'.$dateArray[0].'" AS DATE) AND date_production <= CAST("'.$dateArray[6].'" AS DATE)');
$req = $db->prepare('SELECT AVG(CASE target WHE