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I'm confused about how a parity check will check if the data received is correct. To my understanding it just checks if there is an even or odd number of 1's. Because of this wouldn't it only find an error 50% of the time? Like if I send the number 110011 with an even parity and the last 2 bits get cut off (leaving 1100) wouldn't it still pass the test even though some of the signal was lost?

Tyler Hilbert
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The simple parity check can only detect an odd number of bit errors, but it will detect it 100% of the time.

There are more sophisticated error correction techniques. The Hamming code can detect up to two-bit errors or correct one-bit errors.

I'm not an expert on this.

Torkel Bjørnson-Langen
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  • "Only detecting an odd number of bit errors" is deemed sufficient because the odds of a bit error is like one in a million (so, once per MB). Since it's so rare for a bit to be wrong, the vast majority of the time, this will detect it. For two bits to be wrong in the same byte, the odds about one in a trillion (once per TB). – Mooing Duck Oct 15 '18 at 17:14