     alpha:
         text: "significance level, &alpha;"
         min: -4
-        max: -0.3
+        max: -0.6
         step: 0.01
         value: Math.log10(0.05)
 

    n:
        text: "sample size per group, <em>n</em>"
        min: 2
        max: 1000
        step: 1
        value: 100
    delta:
        text: "effect, &Delta;"
        min: 0

      .y((d) -> yscale[index](d.y))

update_plots = () ->
    svg.selectAll(".curves").remove()

    sigma = +getSliderValue("sigma")
    delta = +getSliderValue("delta")
    n = +getSliderValue("n")
    sem = sigma/Math.sqrt(n)
    df = 2*n-2
    alpha = +getSliderValue("alpha")

    scale4x = d3.scale.linear().domain([0,1]).range([100-sigma*6, 100+delta+sigma*6])
    x = d3.range(npts).map (i) -> scale4x(i/npts)
