174 7 Sequence Similarity Searching Tools
7.5 Exercises
- Ifm= 100andn= 120, 000 , 000 , what normalized bit scoreS′is necessary
to achieve anE-value of 0.01? If theE-value threshold is lowered by 200
times (i.e., lowered to 5 × 10 −^5 ), what normalized bit score is necessary? - The probability of finding exactlykHSPs with a raw scoreSthat is at least
S 0 follows a Poisson distribution. Suppose that the expected number of
HSPs with a raw scoreS≥S 0 is 0. 01. What is the probability of finding no
HSPs with score at leastS 0? What is the probability of finding at least 2
HSPs with score at leastS 0?