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174 7 Sequence Similarity Searching Tools


7.5 Exercises



  1. 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?

  2. 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?

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