text: SELECT
      COUNT(*) as item_count,
      AVG(ochiai_exam_score) as avg_exam_score,
      STD(ochiai_exam_score) as std_exam_score,
      MIN(ochiai_exam_score) as min_exam_score,
      MAX(ochiai_exam_score) as max_exam_score
  FROM ths_results
  WHERE
     IFNULL(ochiai_exam_score, ~0 >> 1) < ~0 >> 1
  AND experiment_id = ?
  AND problem_id IN (
      SELECT problem_id
      FROM ths_results
      WHERE IFNULL(ochiai_exam_score, ~0 >> 1) < ~0 >> 1
      GROUP BY problem_id
      HAVING SUM(experiment_id) = 15
  )
  