I am getting the "Thread 1: Fatal error: Index out of range" in the line where I try to append some value to an array

I am getting a runtime error when I hit the button.

I really hope you have an answer for me

Here is my code

@IBActionfunc Calculate2(_ sender: Any) {
       
        // |Z| - O QUE FALTA FAZER
        var xiNor1 = [Double]()
        var xiNor2 = [Double]()
        var zi1 = [Double]()
        var zi2 = [Double]()
        var x2 = 0.0
        var y2 = 0.0
        let Nn = N.integerValue
        let Mm = M.integerValue
        let sigmaN = Б.doubleValue
        let a = A.doubleValue
        let b = B.doubleValue
        var z = 0.0
        let Ua = 1.96

        for j in 0..            for l in 0..<12 {
                xiNor1.insert( Double(l), at: j)
            }
            xiNor1[j] -= 6;
            zi1[j] = sigmaN * xiNor1[j] + a; // Thread 1: Fatal error: Index out of range
        }
       
        for j in 0..            x2 += zi1[j]
        }
        x2 /= Double(Nn)
       
        for j in 0..            for l in 0..<12 {
                xiNor2.insert( Double(l), at: j)
            }
            xiNor2[j] -= 6;
            zi2[j] = sigmaN * xiNor2[j] + b;
        }
       
        for j in 0..            y2 += zi2[j]
        }
        y2 /= Double(Mm)
       
        z = abs( (x2 - y2) / sqrt( (pow(Double(sigmaN), 2) / Double(Nn)) + (pow(Double(sigmaN), 2) / Double(Mm)) ) )
       
        if (z > Ua) {
            Z.doubleValue = z
            res.stringValue = "H1: mx ≠ my "
        } else {
            Z.doubleValue = z
            res.stringValue = "H0: mx = my"
        }
    }