thank you so much for helping..

Answer 1

Sample mean = ∑x_i ⁄ n = xbar = 16.27

Sample Standard Deviation = (∑x_i - xbar)² ⁄ (n-1) = 5.319993734

90% Confidence Interval : 100% - 90% = 10%

Alpha/2 = .10 ⁄ 2 =.05

Unknown Population Variance (uses Tstat)

T-table: α = .05

DF (n-1) = 9

Tvalue: 1.833

Confidence Interval = xbar ± t_α/2,n-1 (s ⁄ √n)

= 16.27 ± 1.833 (5.319993734 ⁄ √10)

(16.27 - 3.083710402, 16.27 + 3.083710402)

Confidence Interval (13.1863,19.3537)