LoadError in Polychoric Correlation.ipynb

[kozo2]

The output

LoadError: cannot load such file -- statsample/bivariate/polychoric
(pry):3:in `<main>'
/var/lib/gems/2.1.0/gems/pry-0.10.3/lib/pry/pry_instance.rb:355:in `eval'
/var/lib/gems/2.1.0/gems/pry-0.10.3/lib/pry/pry_instance.rb:355:in `evaluate_ruby'
/var/lib/gems/2.1.0/gems/pry-0.10.3/lib/pry/pry_instance.rb:323:in `handle_line'
/var/lib/gems/2.1.0/gems/pry-0.10.3/lib/pry/pry_instance.rb:243:in `block (2 levels) in eval'
/var/lib/gems/2.1.0/gems/pry-0.10.3/lib/pry/pry_instance.rb:242:in `catch'
/var/lib/gems/2.1.0/gems/pry-0.10.3/lib/pry/pry_instance.rb:242:in `block in eval'
/var/lib/gems/2.1.0/gems/pry-0.10.3/lib/pry/pry_instance.rb:241:in `catch'
/var/lib/gems/2.1.0/gems/pry-0.10.3/lib/pry/pry_instance.rb:241:in `eval'
/var/lib/gems/2.1.0/gems/iruby-0.2.9/lib/iruby/backend.rb:65:in `eval'
/var/lib/gems/2.1.0/gems/iruby-0.2.9/lib/iruby/backend.rb:12:in `eval'
/var/lib/gems/2.1.0/gems/iruby-0.2.9/lib/iruby/kernel.rb:87:in `execute_request'
/var/lib/gems/2.1.0/gems/iruby-0.2.9/lib/iruby/kernel.rb:47:in `dispatch'
/var/lib/gems/2.1.0/gems/iruby-0.2.9/lib/iruby/kernel.rb:37:in `run'
/var/lib/gems/2.1.0/gems/iruby-0.2.9/lib/iruby/command.rb:70:in `run_kernel'
/var/lib/gems/2.1.0/gems/iruby-0.2.9/lib/iruby/command.rb:34:in `run'
/var/lib/gems/2.1.0/gems/iruby-0.2.9/bin/iruby:5:in `<top (required)>'
/usr/local/bin/iruby:22:in `load'
/usr/local/bin/iruby:22:in `<main>'

How to reproduce this

1. click launch binder badge in https://github.com/SciRuby/sciruby-notebooks
2. open Polychoric Correlation.ipynb under Statistics directory
3. Run cell