I’m trying to find the standard deviation of average duration in a table for the last 1 day as compared to the last 30 days average duration.

let table1 = view() {
requests | where TimeGenerated > ago(1d) | summarize AvgDuration1d = avg(duration) by itemtype };
let table2 = view() {
requests | where TimeGenerated > ago(30d) | summarize AvgDuration1d = avg(duration) by itemtype }
table1 | join kind=leftouter on itemtype

This above query gives me average duration of both 1 day and 30 days in the same query. Now I need to find the standard deviation between the two.

Any insights may be helpful. TIA!