Soy plants are grown in a green house for 16 days 13 individ

Soy plants are grown in a green house for 16 days. 13 individuals are collected and the stem length of the seedlings are measured in centimeter (avg = 21.3385; s = 1.2190). Calculate a 95% confidence interval for the estimated mean

Solution

Note that              
              
Lower Bound = X - t(alpha/2) * s / sqrt(n)              
Upper Bound = X + t(alpha/2) * s / sqrt(n)              
              
where              
alpha/2 = (1 - confidence level)/2 =    0.025          
X = sample mean =    21.3385          
t(alpha/2) = critical t for the confidence interval =    2.17881283          
s = sample standard deviation =    1.219          
n = sample size =    13          
df = n - 1 =    12          
Thus,              
              
Lower bound =    20.60186567          
Upper bound =    22.07513433          
              
Thus, the confidence interval is              
              
(   20.60186567   ,   22.07513433   ) [ANSWER]