Error detection in digital communication — understanding parity checking Which of the following statements best describes the parity method of error detection used during code transmission between two locations?

Introduction / Context:
Parity checking is a classic, low-cost error-detection technique widely used in memory systems and serial links. It appends one extra bit (parity bit) to a data word so that the total number of 1s becomes either even (even parity) or odd (odd parity). This question tests whether you know what kind of errors parity can reliably detect and what it cannot.

Given Data / Assumptions:

• The channel might flip bits during transmission.
• Only a single parity bit is added to each data word.
• No additional redundancy (like CRC or ECC) is present.

Concept / Approach:
Parity adds one bit to enforce a parity rule. If exactly one bit in the data word flips, the total number of 1s no longer satisfies the rule and the receiver flags an error. However, if two bits flip, the parity may still appear correct (an even number of errors can cancel out), so parity cannot reliably detect double-bit errors, nor can it locate or correct any error by itself.

Step-by-Step Solution:

Verification / Alternative check:
Try a concrete example: with even parity, data 1011 (three 1s) gets parity 1 to make total 4 (even). If one bit flips, total becomes odd → error detected. If two bits flip, total returns to even → error can slip through.

Why Other Options Are Wrong:

• Double-bit detection (option a): parity cannot guarantee detection of two errors.
• Not suitable for single-bit errors (option b): the opposite is true; it is ideal for single-bit error detection.
• Detecting and correcting (option d): correction needs codes like Hamming; parity only detects.

Common Pitfalls:
Confusing detection with correction; assuming parity works for all multi-bit errors; forgetting that parity gives zero information about which bit flipped.

Final Answer:
Parity checking is best suited for detecting single-bit errors in transmitted codes.