Use normal sampling distributions and standard errors
Use exact values. X̄ denotes the random sample mean; x̄ is one realised value
X₁,...,Xₙ are independent observations from the same normal population. The second normal parameter below is the variance
\[X_i\sim N(6,25),\qquad n=64,\qquad\overline X=\frac1n\sum_{i=1}^nX_i\]