Add confidence_intervals.rb from core, and update it to use Statistics3

[benrfairless]

Relevant issue(s)

Fixes #965

What does this do?

• Creates the confidence_intervals.rb file
• Updates L25 to use Statistics3 instead of Statistics2

Why was this needed?

To resolve the bug in #965

Implementation notes

• Deployment should occur on the host by running the below command as deploy: bundle exec rails themes:install

Screenshots

Nil

Notes to reviewer

This change won't make any impact in staging or test due to the number of records required to make it happen.

[Br3nda]

is this code from upstream? I ask because the commit is yours, Ben, and we need to make sure we track this if we pull/branch from upstream again on the next alaveteli version

[benrfairless]

The code in core is here: https://github.com/openaustralia/alaveteli/blob/production/lib/confidence_intervals.rb
It fixes this commit which only updated L1, not L25.

[Br3nda]

if you ran bundle exec rubocop -a on that new ruby file it would probably all pass CI

[Br3nda]

(oops, wrong button)

[benrfairless]

if you ran bundle exec rubocop -a on that new ruby file it would probably all pass CI

I can't do that on my machine at the moment because I can't run bundle install on Ruby 2.7.8 on my Mac.