Using BigQuery to find outliers with standard deviation results combined with WHERE clause - statistics

Question

Standard deviation analysis can be a useful way to find outliers. Is there a way to incorporate the result of this query (finding the value of the fourth standard deviation away from the mean)...
SELECT (AVG(weight_pounds) + STDDEV(weight_pounds) * 4) as high FROM [publicdata:samples.natality];
result = 12.721342001626912
...Into another query that produces information about which states and dates have the most babies born heavier that 4 standard deviations from average?
SELECT state, year, month ,COUNT(*) AS outlier_count
FROM [publicdata:samples.natality]
WHERE
(weight_pounds > 12.721342001626912)
AND
(state != '' AND state IS NOT NULL)
GROUP BY state, year, month
ORDER BY outlier_count DESC;
Result:
Row state year month outlier_count
1 MD 1990 12 22
2 NY 1989 10 17
3 CA 1991 9 14
Essentially it would be great to combine this into a single query.

Answer 1

You can abuse JOIN for this (and thus performance will suffer):
SELECT n.state, n.year, n.month ,COUNT(*) AS outlier_count
FROM (
SELECT state, year, month, weight_pounds, 1 as key
FROM [publicdata:samples.natality]) as n
JOIN (
SELECT (AVG(weight_pounds) + STDDEV(weight_pounds) * 4) as giant_baby,
1 as key
FROM [publicdata:samples.natality]) as o
ON n.key = o.key
WHERE
(n.weight_pounds > o.giant_baby)
AND
(n.state != '' AND n.state IS NOT NULL)
GROUP BY n.state, n.year, n.month
ORDER BY outlier_count DESC;