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
sample mean +/- t_crit x SEM
= 25.25 +/- 2.059538553 x 0.073543551
= [25.099 to 25.401]
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