<invoke name="query_sql"> <parameter name="sql">SELECT 'ALL' AS grp, COUNT(*) AS n, corr(sepal_length, sepal_width) AS corr_sepal_len_width, corr(petal_length, sepal_width) AS corr_petal_len_sepal_width FROM raw.iris UNION ALL SELECT species, COUNT(*), corr(sepal_length, sepal_width), corr(petal_length, sepal_width) FROM raw.iris GROUP BY species</parameter> <parameter name="purpose">Check for Simpson's paradox: overall vs within-species correlation of sepal length and width</parameter> <parameter name="source">raw</parameter> </invoke> ˋˋˋ