How to identify if Rows that have a matching value - does a specific column also have matching data?

[Grimes65]

I need a formula that will tell me for each row that has a value of "1" in column A - do the values in column B match? (i.e. For all numbers that say "1" column B should say expired for all of those, however in this example there is 1 line item that does not match, it says "not expired". Technically, they should all match but they do not - I need to easily know the line items that have ones that don't match. Number 4 in column A is perfect because column b matches for both those line items. 

Example data 

Number	Reason
1	expired
1	not expired
1	expired
1	expired
3	good
3	bad
3	bad
2	forget
2	forget
4	expired
4	expired

[#2 · Accepted solution]

@Grimes65 

Enter the following formula in C2, then fill down:

=COUNTA(UNIQUE(FILTER($B$2:$B$10000, $A$2:$A$10000=A2)))>1

This will return TRUE for the rows of numbers with more than one unique problem.

You can sort or filter on column C if desired.