Sqlite get the deviation value

please, could you help me? I have this query:

SELECT RESULT_TIMESTAMP,COMMAND_DESC, TYPERESULT_NAME,RESULT_DESC,RESULT_CODE,
MIN(RESULT_TIMESTAMP) AS MIN,
MAX(RESULT_TIMESTAMP) AS MAX,
AVG(RESULT_TIMESTAMP) AS AVG,
FROM V_RESULT 
WHERE TESTRESULT_FILE = 'file_02'
GROUP BY COMMAND_DESC

I have the avg value and the column values of "typeresult_name" can be "ok", "error" or "skip". What I need is another column with the deviation value from the RESULT_TIMESTAMP column which TYPERESULT_NAME be="OK".

Thanks!