选择恰当的单词将短文补充完整。

     Emily has so many   1    at home. She has to do her homework   2    school. She

can't go   3   on school nights. She has to wash the dishes(洗碗)after   4   , and then

she  can  watch  TV    5    an  hour.  She  likes   6   . She usually does some reading

at night. She has to be in     7    by  ten  o'clock  because  she  has  to   8    up  early

the next morning. She   9    a music club and often goes there on weekends. She has

to    10   her guitar every day. But she doesn't think she's unhappy.

已知x₁，x₂，…，x_n的方差为2，则3x₁+5，3x₂+5，…，3x_n+5的标准差为______．