Error:attempt to index local 'part' (a nil value). Help?

I'm pretty new to scripting and I'm having a problem:

local speedBoost = script.Parent

local function steppedOn(part)
	**local parent = part.Parent**
	if game.Players:GetPlayerFromCharacter(parent) then
		parent.Humanoid.WalkSpeed = 100
		wait(10)
		parent.Humanoid.WalkSpeed = 16
	end
	
end
speedBoost.Touched:Connect(steppedOn())

The Error: ** 13:54:39.433 - Workspace.Power-Up.Script:4: attempt to index local 'part' (a nil value)**

I have no idea how to fix it.

I don't know if its just that part I need to fix or I just suck at scripting.

Any Ideas?