Since we don't know the population standard deviation, only that for the sample, we should use a t-distribution here, with df = n-1 = 25. The critical t-stat for a 95% confidence interval will be:

t_crit = t.inv(p=0.975,df=25) = 2.059538553

The standard error is sample sd / sqrt(n) = 0.375/sqrt(26)

SEM = 0.073543551

So the 95% confidence interval for the sample mean is given by