已知泊松分布或正态分布的累积概率值，如何用matlab求出其分位点

Question

例如，已知某随机变量服从lambda为5的泊松分布，b=0.7211 查泊松分布表可知，当x=6时，累积概率=0.7621 离0.7211最接近，怎么用matlab返回6这个值呢？同样地，对于服从正态分布，已知F（y）=0.662 怎么用matlab返回y的值呢？还有对于均匀分布，指数分布的类似问题，如何同matlab解决呢？

Answer 1

>> poissinv(0.7211,5)

ans =

6

Critical Values of Distribution functions.
betainv - Beta inverse cumulative distribution function.
binoinv - Binomial inverse cumulative distribution function.
chi2inv - Chi square inverse cumulative distribution function.
evinv - Extreme value inverse cumulative distribution function.
expinv - Exponential inverse cumulative distribution function.
finv - F inverse cumulative distribution function.
gaminv - Gamma inverse cumulative distribution function.
geoinv - Geometric inverse cumulative distribution function.
gevinv - Generalized extreme value inverse cumulative distribution function.
gpinv - Generalized Pareto inverse cumulative distribution function.
hygeinv - Hypergeometric inverse cumulative distribution function.
icdf - Specified inverse cumulative distribution function.
logninv - Lognormal inverse cumulative distribution function.
nbininv - Negative binomial inverse distribution function.
ncfinv - Noncentral F inverse cumulative distribution function.
nctinv - Noncentral t inverse cumulative distribution function.
ncx2inv - Noncentral Chi-square inverse distribution function.
norminv - Normal (Gaussian) inverse cumulative distribution function.
poissinv - Poisson inverse cumulative distribution function.
raylinv - Rayleigh inverse cumulative distribution function.
tinv - T inverse cumulative distribution function.
unidinv - Discrete uniform inverse cumulative distribution function.
unifinv - Uniform inverse cumulative distribution function.
wblinv - Weibull inverse cumulative distribution function.