The Slope Coefficient equals sample average?

[Sartorial]

From Kaplan:

So in Level 2 Quant, the slope coefficient takes the place of the sample mean in the equation?

Hence that is how you find the interval.

[S2000magician]

@Sartorial

So in Level 2 Quant, the slope coefficient takes the place of the sample mean in the equation?

In essence, yes.