Getting an attr_accessor to work

I have a user model with a number of fields representing the user
profile.

When a user is first signing up, I have an initial question I want to
ask
that is a one time and not part of the user profile.

In the model, I have:
attr_accessor :completed_cfdym
validates(:completed_cfdym, inclusion: { in: [‘Yes’, ‘No’], message:
“%{value} is not a valid response”} )

In the view, I have:

<% f.label :completed_cfdym, "Have you Completed 'A Conversation for

The Difference You Make’", class: ‘span5’ %>
<%= f.select :completed_cfdym, {’’ => nil, ‘Yes’ => ‘Yes’, ‘No’ =>
‘No’}, {}, { :class => ‘span1’ } %>

In the controller, in the create method, I have:

if params[:completed_cfdym] == 'Yes'
    Conversation.create_holder(@user)
end

Looking at the console model in the development environment, I see that
completed_cfdym is returning nil, ‘Yes’, or ‘No’ based on what I select.

However:

The validation fails and, when it returns to the forms page, the
completed_cfdym is not preserved - it always returns to ‘’

Also, if I remove the validates, the test in the controller does not
seem
to be able to recognize the ‘Yes’.

What am I missing?