问题如下图：
选项：
A. 
B. 
C. 
老师 narrow的是confidence level吗？ 解释：
NO.PZ2017092702000111 问题如下 For a two-siconfininterval, increase in the gree of confinwill result in: A.a wir confininterval. B.a narrower confininterval. C.no change in the wih of the confininterval. A is correct. the gree of confinincreases (e.g., from 95% to 99%), a given confinintervwill become wir. A confinintervis a range for whione cassert with a given probability 1 – α, callethe gree of confince, thit will contain the parameter it is intento estimate.随着置信度的增加（例如，从 95% 到 99%），给定的置信区间将变得更宽。 置信区间是一个范围，人们可以以给定的概率 1 – α（称为置信度）并代表它会包含我们要估计的参数。 我理解的两个概念confinintervalμ±δconfinlevel/gree置信度，为68%、90%……etc.所以这道题我选了B，求解答
NO.PZ2017092702000111 问题如下 For a two-siconfininterval, increase in the gree of confinwill result in: A.a wir confininterval. B.a narrower confininterval. C.no change in the wih of the confininterval. A is correct. the gree of confinincreases (e.g., from 95% to 99%), a given confinintervwill become wir. A confinintervis a range for whione cassert with a given probability 1 – α, callethe gree of confince, thit will contain the parameter it is intento estimate.随着置信度的增加（例如，从 95% 到 99%），给定的置信区间将变得更宽。 置信区间是一个范围，人们可以以给定的概率 1 – α（称为置信度）并代表它会包含我们要估计的参数。 置信度增加，不是应该估计越准确吗？
NO.PZ2017092702000111问题如下For a two-siconfininterval, increase in the gree of confinwill result in:A.a wir confininterval. B.a narrower confininterval. C.no change in the wih of the confininterval. A is correct. the gree of confinincreases (e.g., from 95% to 99%), a given confinintervwill become wir. A confinintervis a range for whione cassert with a given probability 1 – α, callethe gree of confince, thit will contain the parameter it is intento estimate.随着置信度的增加（例如，从 95% 到 99%），给定的置信区间将变得更宽。 置信区间是一个范围，人们可以以给定的概率 1 – α（称为置信度）并代表它会包含我们要估计的参数。 是不是混淆了gree of freem ,if increase of gree of freem, confininternwill become narrower? T stribution will become Z stribution?
NO.PZ2017092702000111 老师，如果是t分布的话，这题的confinlevel是否会缩窄
如果是单尾的话就会缩小置信区间吗？
