
1. Re: 95% CIs  How do they work?
Shinichiro Murakami Jan 10, 2018 4:53 PM (in response to Dan Bartels)Hi Dan
We need your data to investigate.
Could you please attach packaged workbook.
Regards,
Shin

2. Re: 95% CIs  How do they work?
Liana CrisanVandeborne Mar 15, 2018 11:53 AM (in response to Shinichiro Murakami)Without having your data, I cannot figure out what you are trying to do.
But picking up from the main knowledge base article: Creating Error Bars or CI Bars: http://kb.tableau.com/articles/HowTo/creatingerrorbars
You could update your file to display the confidence intervals around the average or around the mean. I used the Error or CI Bars.twbx and created 2 additional worksheets. I included the formulas for the CI around the mean and around the median, depending what you choose to display. Then I used those values to add bands to the viz, per cell (one of your examples seems to be per pane). You will see that the values used as margins for the bands are the calculated fields.
95% Lower_AVG
AVG([Sales] )(1.96*((STDEV([Sales])/SQRT(sum([Number of Records] )1) )))
95% Upper_AVG
AVG([Sales] )+(1.96*((STDEV([Sales])/SQRT(sum([Number of Records] )1) )))
Or
95% Lower_MEDIAN
MEDIAN([Sales] )(1.96*((STDEV([Sales])/SQRT(sum([Number of Records] )1) )))
95% Upper_MEDIAN
MEDIAN([Sales] )+(1.96*((STDEV([Sales])/SQRT(sum([Number of Records] )1) )))
Here is the link to this workbook in my public account:

3. Re: 95% CIs  How do they work?
nick masca Jan 23, 2019 6:32 AM (in response to Dan Bartels)Hi Dan,
You appear to have misunderstood what a confidence interval represents  there is a simple explanation of what confidence intervals are here: Confidence Intervals.
It sounds like you actually want to display error bars relating to the 2.5% and 97.5% percentiles, which would show the range of values in which 95% of your data lie within. Alternatively, you could consider showing a boxplot instead, which provides similar information about the distribution of your data.
Cheers,
Nick