How to Calculate value of one column based on values in another column

[Jairacha]

Hi - I'm trying to derive the value of Col.C (below) based on the values in Col.B (below) for each record in Col.A (below). I would like to accomplish this using the formula tool. 

Example:

In the table below, I would like to flip all the values in Col.C to "Yes" only IF Col.B has both "Yes" and "No" for each record in Col.A (X, Y, Z). So if and only if I have a "Yes" and "No" for the record "X" in Col.A, then the values in Col.C would be "Yes" for the record "X". If all the values in for a record in Col.A ("Y") are "Yes" then the values in Col.C should be "Yes". If all the values in for a record in Col.A ("Z") are "No" then the values in Col.C should be "No". 

Col.A	ColB.	Col. C (calculated)
X	Yes	Yes
X	Yes	Yes
X	No	Yes
X	Yes	Yes
Y	Yes	Yes
Y	Yes	Yes
Y	Yes	Yes
Z	No	No
Z	No	No
Z	No	No
Z	No	No
Z	No	No

Appreciate the help with this!!

[DataNath · Accepted solution]

Hey @Jairacha there's a few variations of doing this but here's one. We just use a Summarize tool with the 'Longest' string method, grouped by [Col.A], and then join this back to the starting dataset: