TRICKY DAX Calculated Column Measures

Hey Anonymous , I received a request regarding confidence intervals with Kaplan Meier survival curves from Anonymous and so I was working on it and came up with the following answer:

OK, following along from this:

http://www.real-statistics.com/survival-analysis/kaplan-meier-procedure/confidence-interval-for-the-...

And if you are following my article here:

https://community.powerbi.com/t5/Community-Blog/Kaplan-Meier-Survival-Curves-with-Power-BI-Part-2/ba...

Then in your KMDeptDaysAll table, create this measure:

ci_alpha = 0.05

This is your confidence interval, in this case 95%

And then create these columns:

ci_S(t) = 
VAR __table = FILTER(ALL(KMDeptDaysAll),[Department] = EARLIER([Department]) && [Days] <= EARLIER([Days]))
RETURN
PRODUCTX(__table,[1-e_i/d_i])

ci_se_1 = 
VAR __calc = [e_i] / ([d_i] * ([d_i] - [e_i]))
RETURN
IF(ISERROR(SQRT(__calc)),BLANK(),[ci_S(t)] * SQRT(__calc))

ci_se = 
VAR __table = FILTER(ALL(KMDeptDaysAll),[Department] = EARLIER([Department]) && [Days] <= EARLIER([Days]))
VAR __sum = SUMX(__table,[ci_se_1])
RETURN
[ci_S(t)] * __sum

ci_lower = 
[ci_S(t)] ^ IF(ISERROR(EXP(NORM.S.INV([ci_alpha]/2)/IF(ISERROR(LN([ci_S(t)])),BLANK(),LN([ci_S(t)])*[ci_se]/[ci_S(t)]))),BLANK(),EXP(NORM.S.INV([ci_alpha]/2)/IF(ISERROR(LN([ci_S(t)])),BLANK(),LN([ci_S(t)])*[ci_se]/[ci_S(t)])))

ci_upper = 
[ci_S(t)] ^ IF(ISERROR(EXP(-NORM.S.INV([ci_alpha]/2)/IF(ISERROR(LN([ci_S(t)])),BLANK(),LN([ci_S(t)])*[ci_se]/[ci_S(t)]))),BLANK(),EXP(-NORM.S.INV([ci_alpha]/2)/IF(ISERROR(LN([ci_S(t)])),BLANK(),LN([ci_S(t)])*[ci_se]/[ci_S(t)])))

Can't be certain this is all 100% correct as the original article I was working from didn't have confidence intervals. Will try to do some verification work on this.