= Triweight kernel
{title2=$K(x)=\frac{35}{32}(1-x^2)^3\mathbf1_{|x|<1}$}
The triweight kernel is a compactly supported symmetric <probability> <probability density function>[density] with <variance> $1/9$. Its value and first two <derivatives> vanish at the support endpoints. Its integrated squared <second derivative> is $35$, and it minimizes that curvature among twice continuously differentiable <probability density functions>[densities] with zero <mean> and the same <variance>, by the <triweight density minimizes integrated squared curvature> inequality.
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