If nCk represents the number of ways k parts can be chosen from a pool of n, the probability of interest is the complement of the probability of selecting all good parts.
1 - (167C3)/(170C3) = 42,085/804,440 ≈ 0.0523
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nCk = n!/(k!(n-k)!)
7.83 x 10^-7 (the *^* is where the power goes)