Answer:
Estimated number of indigenous faults remaining undetected is 6
Explanation:
The maximum likelihood estimate of indigenous faults is given by,
[tex]N_F=n_F\times \frac{N_S}{n_S}[/tex] here,
[tex]n_F[/tex] = the number of unseeded faults = 6
[tex]N_S[/tex] = number of seeded faults = 30
[tex]n_s[/tex] = number of seeded faults found = 15
So NF will be calculated as,
[tex]N_F=6\times \frac{30}{15}=12[/tex]
And the estimate of faults remaining is [tex]N_F-n_F[/tex] = 12 - 6 = 6