instruction: what is the average cost in a hospital involving a laboratory test for mcv during the previous year?
response: SELECT AVG(t1.c1) FROM (SELECT SUM(cost.cost) AS c1 FROM cost WHERE cost.hadm_id IN (SELECT labevents.hadm_id FROM labevents WHERE labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'mcv')) AND DATETIME(cost.chargetime, 'start of year') = DATETIME(CURRENT_TIME(), 'start of year', '-1 year') GROUP BY cost.hadm_id) AS t1