# Computer Science - Networking - Discussion

Discussion Forum : Networking - Section 1 (Q.No. 3)
3.
The probability that a single bit will be in error on a typical public telephone line using 4800 bps modem is 10 to the power -3. If no error detection mechanism is used, the residual error rate for a communication line using 9-bit frames is approximately equal to
0.003
0.009
0.991
0.999
None of the above
Explanation:
No answer description is available. Let's discuss.
Discussion:
9 comments Page 1 of 1.

Shivakumar_bpt said:   7 years ago
Probability that a single bit is in error 10^-3 = 0.001t.

Probability that a single bit is not in error = 1 - 0.001 = 0.999.

Geetu said:   8 years ago
Please tell me how can I easily solve?

Here the data rate of 4800 bps is redundant information.
Probability that a single bit is in error 10^-3 = 0.001t
Probability that a single bit is not in error = 1 - 0.001 = 0.999

In a frame of 9 bits the residual error rate value signifies the probability that at least one of the bits out of the nine is in error.

Thus, chances that all 9 bits are correct = 0.999^9 = 0.991 (approx)
Residual error rate = chances that at least one of 9 bits is incorrect = 1 - 0.991 = 0.009 (approx)
(2)

Thus, chances that all 9 bits are correct = 0.999*9 = 0.991 (approx)

Residual error rate = chances that at least one of 9 bits is incorrect = 1 - 0.991 = 0.009 (approx)
(1)

Here the data rate of 4800 bps is redundant information.
Probability that a single bit is in error 10^-3 = 0.001t
Probability that a single bit is not in error = 1 - 0.001 = 0.999

In a frame of 9 bits the residual error rate value signifies the probability that at least one of the bits out of the nine is in error.

Thus, chances that all 9 bits are correct = 0.999^9 = 0.991 (approx)
Residual error rate = chances that at least one of 9 bits is incorrect = 1 - 0.991 = 0.009 (approx)

Dipayan Das said:   1 decade ago
1bit error probability 1/1000
9bit error probability 9/1000

.ie .009

Suresh kumar said:   1 decade ago
What is the method/theory to solve this question?