Good- Turing:举例 例如:记住:p、w)=(c(w)+1)*N(c(w)+1)(T*N(c(w) T: <s>what is it what lI? T=8 V=(what, iS, it, small, ? <S>, flying, birds, are, a, bird,, VE p(it)=0.125,p(wha=0.25,p()=0,p( what is it?)=0.252*0.1252≈0.001 p( (it is flying=0.125*0.25*02=0 重新计算(N(0=6,N1)=4N(2)=2,Ni=0当论2) P(it)=(1+1)*N(1+1)/(8*N(1)2*2(8*4)=0.125 P(wha=(2+1)*N(2+1)(8*N(2)=3*O0(8*2)=0: keep orig. p(what P()=(0+1)*N(0+1)(8*N(O)=1*4/(8*6)0083 归一化(除以15=∑。P())并计算 p(it)≈0.08,p(wha)≈0.17,p()≈0. p( what is it?)=01752*0.0820.0002 p( (it is flying)≈0.08*0.17*0.062≈0.00004Good-Turing: 举例 • 例如：记住： pr (w)=(c(w)+1)*N(c(w)+1)/(|T|*N(c(w))) – T: <s>what is it what is small? |T|=8 – V={what,is,it,small,?,<s>,flying,birds,are,a,bird,.}, |V|=12 p(it)=0.125,p(what)=0.25,p(.)=0,p(what is it?)=0.252*0.1252≈0.001 p(it is flying.)=0.125*0.25*02=0 – 重新计算（N(0)=6,N(1)=4,N(2)=2,N(i)=0 当 i>2）: Pr (it)=(1+1)*N(1+1)/(8*N(1))=2*2/(8*4)=0.125 Pr (what)=(2+1)*N(2+1)/(8*N(2))=3*0/(8*2)=0: keep orig. p(what) Pr (.)=(0+1)*N(0+1)/(8*N(0))=1*4/(8*6)≈0.083 – 归一化（除以 1.5= ）并计算 p’(it) ≈ 0.08, p’(what) ≈ 0.17, p’(.) ≈ 0.06 p’(what is it?)=01752*0.082≈0.0002 p’(it is flying.) ≈ 0.08*0.17*0.062 ≈0.00004  | | ( ) w V pr w