Shell Programming and Scripting

I need some help with a script which accepts multiple rows of input (analysis from a virtual robot's testrun) from the standard in, and compares it as a whole with another file featuring erroneous data from a virtual robot's test run. What I want it to be able to do is slice off all the erroneous data featured in this file from the input and leave only the successful test data.
So far, I've had an attempt at this:

Code:

errors=$(cat ErroneousData)
while read I
do
if [ "$I" = "$errors" ] 
then
 Z="$I" - "$errors"
fi
echo "$Z"
done

Yet whenever I try to run this script with the input, nothing is output, so there are faults within the script for sure, but I can't figure out what... Cheers!

Code:

while read I
do
echo "$I" > tmp
grep -v -f ErroneousData tmp
done

Great, it works perfectly now. Thanks!