Given that the mean is $9.5 and the standard deviation is $1.30, the standard error will be given by: σ/√n where σ-standard deviation n=sample size
thus, we shal have: 1.30/√20 =0.2906 Next we find the margin error 0.2906*2=0.581 thus the confidence interval will be: (9.5+0.581, 9.5-0.581) =(10.081,8.919)
