Methods of operating nonvolatile memory devices include testing a plurality of strings of nonvolatile memory cells in the memory device to identify at least one weak string therein having a higher probability of yielding erroneous read data error relative to other ones of the plurality of strings. An identity of the at least one weak string may be stored as weak column information. This weak column information may be used to facilitate error detection and correction operations. In particular, an error correction operation may be performed on a first plurality of bits of data read from the plurality of strings using an algorithm that modifies a weighting of the reliability of one or more data bits in the first plurality of bits of data based on the weak column information. More specifically, an algorithm may be used that interprets a bit of data read from the at least one weak string as having a relatively reduced reliability relative to other ones of the first plurality of data bits.