$121.2±2.262\frac{11.1}{\sqrt{10}}=121.2±7.94=\left(113.3,\text{\hspace{0.17em}}129.1\right)$

Description:

Math equation. If one plugs the t-value of 2.262 into the equation, the resulting 95% confidence interval ranges from 113.3 to 129.1.