求數神解答以下問題?

35.
σXbar = σ / √n

σ
= σXbar * √n
= 3 * √16
= 3 * 4
= 12 , 選 d ... Ans

36.
σXbar = σ / √n = 16 / √64 = 16/8 = 2

P( 97 < Xbar < 106 )
= P( (97-100)/2 < Z < (106-100)/2 )
= P( - 1.5 < Z < 3 )
= P( Z < 3 ) - P( Z < - 1.5 )
= ( 1 - 0.00135 ) - 0.0668
≒ 0.9319 , 選 c ... Ans

37.
P( x < 9 )
= P( Z < (9-20)/4 )
= P( Z < - 2.75 )
= 0.003 , 選 c ... Ans

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