b问怎么看出来The sample mean is already unbiased?

NO.PZ2020010304000035问题如下experiment yiel the following tIt is hypothesizeththe ta comes from a uniform tribution, U(0, b). Calculate the sample meanvariance. Whare the unbiaseestimators of the meanvariance?Calculate the b in U(0, using the formula for the meof a uniform stribution anthe value of the unbiasesample mefounin part b. Calculate the b in U(0, using the formula for the varianof a uniform stribution anthe value of the unbiasesample varianfounin part b.Use the stanrformuto get the sample variance(here, n=15)μ=n−1∑i=1nXi=0.39\mu = n^{-1}\sum_{i=1}^{n}X_i =0.39μ=n−1∑i=1n​Xi​=0.39σ2=n−1∑i=1n(Xi−μ)2=0.08\sigma^2 = n^{-1}\sum_{i=1}^{n}{(X_i-\mu)}^2 =0.08σ2=n−1∑i=1n​(Xi​−μ)2=0.08b.The sample meis alrea unbiaseFor the variance:s2=nσ2/(n−1)=15∗0.080/14=0.086s^2=n\sigma^2/(n-1) =15*0.080/14=0.086s2=nσ2/(n−1)=15∗0.080/14=0.086c.The mefor a U(a,stribution is given as: μ=(a+b)/20.385=(0+b)/2b=0.77 The varianfor a U(a,stribution is given as: σ2=(b−a)2/12\sigma^2=(b-a)^2/12σ2=(b−a)2/120.086=b2/120.086=b^2/120.086=b2/12b=1.016b=1.016b=1.016老师您看我写的不明白的地方总体方差不应该是（样本方差的均值*15）/14吗？

NO.PZ2020010304000035 问题如下 experiment yiel the following tIt is hypothesizeththe ta comes from a uniform tribution, U(0, b). Calculate the sample meanvariance. Whare the unbiaseestimators of the meanvariance?Calculate the b in U(0, using the formula for the meof a uniform stribution anthe value of the unbiasesample mefounin part b. Calculate the b in U(0, using the formula for the varianof a uniform stribution anthe value of the unbiasesample varianfounin part Use the stanrformuto get the sample variance(here, n=15)μ=n−1∑i=1nXi=0.39\mu = n^{-1}\sum_{i=1}^{n}X_i =0.39μ=n−1∑i=1n​Xi​=0.39σ2=n−1∑i=1n(Xi−μ)2=0.08\sigma^2 = n^{-1}\sum_{i=1}^{n}{(X_i-\mu)}^2 =0.08σ2=n−1∑i=1n​(Xi​−μ)2=0.08b.The sample meis alrea unbiaseFor the variance:s2=nσ2/(n−1)=15∗0.080/14=0.086s^2=n\sigma^2/(n-1) =15*0.080/14=0.086s2=nσ2/(n−1)=15∗0.080/14=0.086c.The mefor a U(a,stribution is given as: μ=(a+b)/20.385=(0+b)/2b=0.77 The varianfor a U(a,stribution is given as: σ2=(b−a)2/12\sigma^2=(b-a)^2/12σ2=(b−a)2/120.086=b2/120.086=b^2/120.086=b2/12b=1.016b=1.016b=1.016 总体是Uniform的话，样本一定是uniform吗？如果是的话，可以用（0.95-0）/2来计算样本均值吗

NO.PZ2020010304000035问题如下experiment yiel the following tIt is hypothesizeththe ta comes from a uniform tribution, U(0, b). Calculate the sample meanvariance. Whare the unbiaseestimators of the meanvariance?Calculate the b in U(0, using the formula for the meof a uniform stribution anthe value of the unbiasesample mefounin part b. Calculate the b in U(0, using the formula for the varianof a uniform stribution anthe value of the unbiasesample varianfounin part b.Use the stanrformuto get the sample variance(here, n=15)μ=n−1∑i=1nXi=0.39\mu = n^{-1}\sum_{i=1}^{n}X_i =0.39μ=n−1∑i=1n​Xi​=0.39σ2=n−1∑i=1n(Xi−μ)2=0.08\sigma^2 = n^{-1}\sum_{i=1}^{n}{(X_i-\mu)}^2 =0.08σ2=n−1∑i=1n​(Xi​−μ)2=0.08b.The sample meis alrea unbiaseFor the variance:s2=nσ2/(n−1)=15∗0.080/14=0.086s^2=n\sigma^2/(n-1) =15*0.080/14=0.086s2=nσ2/(n−1)=15∗0.080/14=0.086c.The mefor a U(a,stribution is given as: μ=(a+b)/20.385=(0+b)/2b=0.77 The varianfor a U(a,stribution is given as: σ2=(b−a)2/12\sigma^2=(b-a)^2/12σ2=(b−a)2/120.086=b2/120.086=b^2/120.086=b2/12b=1.016b=1.016b=1.016样本均值应等于A加B然后除以2；无偏均值就是该均值。样本方差等于B减去A 平方然后除以12。解题公式不知道什么意思。最后两问不知道在说什么。均匀分布到底应该怎么计算？谢谢。尤其是最后两个问题在说什么。感觉均匀分布前提和适用场景特别不清楚。烦请详细说明，谢谢

NO.PZ2020010304000035问题如下 experiment yiel the following tIt is hypothesizeththe ta comes from a uniform tribution, U(0, b). Calculate the sample meanvariance. Whare the unbiaseestimators of the meanvariance?Calculate the b in U(0, using the formula for the meof a uniform stribution anthe value of the unbiasesample mefounin part b. Calculate the b in U(0, using the formula for the varianof a uniform stribution anthe value of the unbiasesample varianfounin part b.Use the stanrformuto get the sample variance(here, n=15)μ=n−1∑i=1nXi=0.39\mu = n^{-1}\sum_{i=1}^{n}X_i =0.39μ=n−1∑i=1n​Xi​=0.39σ2=n−1∑i=1n(Xi−μ)2=0.08\sigma^2 = n^{-1}\sum_{i=1}^{n}{(X_i-\mu)}^2 =0.08σ2=n−1∑i=1n​(Xi​−μ)2=0.08b.The sample meis alrea unbiaseFor the variance:s2=nσ2/(n−1)=15∗0.080/14=0.086s^2=n\sigma^2/(n-1) =15*0.080/14=0.086s2=nσ2/(n−1)=15∗0.080/14=0.086c.The mefor a U(a,stribution is given as: μ=(a+b)/20.385=(0+b)/2b=0.77 The varianfor a U(a,stribution is given as: σ2=(b−a)2/12\sigma^2=(b-a)^2/12σ2=(b−a)2/120.086=b2/120.086=b^2/120.086=b2/12b=1.016b=1.016b=1.016​a求的是sample variance，为什么分母不是除以n-1 呢？

NO.PZ2020010304000035问题如下experiment yiel the following tIt is hypothesizeththe ta comes from a uniform tribution, U(0, b). Calculate the sample meanvariance. Whare the unbiaseestimators of the meanvariance?Calculate the b in U(0, using the formula for the meof a uniform stribution anthe value of the unbiasesample mefounin part b. Calculate the b in U(0, using the formula for the varianof a uniform stribution anthe value of the unbiasesample varianfounin part b.Use the stanrformuto get the sample variance(here, n=15)μ=n−1∑i=1nXi=0.39\mu = n^{-1}\sum_{i=1}^{n}X_i =0.39μ=n−1∑i=1n​Xi​=0.39σ2=n−1∑i=1n(Xi−μ)2=0.08\sigma^2 = n^{-1}\sum_{i=1}^{n}{(X_i-\mu)}^2 =0.08σ2=n−1∑i=1n​(Xi​−μ)2=0.08b.The sample meis alrea unbiaseFor the variance:s2=nσ2/(n−1)=15∗0.080/14=0.086s^2=n\sigma^2/(n-1) =15*0.080/14=0.086s2=nσ2/(n−1)=15∗0.080/14=0.086c.The mefor a U(a,stribution is given as: μ=(a+b)/20.385=(0+b)/2b=0.77 The varianfor a U(a,stribution is given as: σ2=(b−a)2/12\sigma^2=(b-a)^2/12σ2=(b−a)2/120.086=b2/120.086=b^2/120.086=b2/12b=1.016b=1.016b=1.016第三问和第四问求具体解析及教程是哪一页有讲到啊？