Skill: inference
Inference Calculator
Build and interpret confidence intervals, set up hypotheses, compute test statistics and p-values, and conclude without overclaiming.
1 Confidence interval builder
Enter summary statistics and a confidence level; get the interval and its margin.
Results
Enter values and press Build interval.
2 z-test calculator
z = (x̄ − μ0)/(σ/√n), with one- and two-sided p-values.
Results
Enter values and press Test.
(function(){ function num(id){ var v = parseFloat(document.getElementById(id).value); return isNaN(v) ? 0 : v; } function r4(x){ return Math.round(x * 10000) / 10000; } document.getElementById('iGo').addEventListener('click', function(){ var est = num('iEst'), sig = num('iSig'), n = Math.round(num('iN')); var lvl = document.getElementById('iLvl').value; var res = document.getElementById('iResult'), steps = document.getElementById('iSteps'); res.style.display = 'block'; if (n < 2 || sig <= 0){ res.innerHTML = '
Need n \u2265 2 and \u03c3 > 0.
'; return; } var r = TOOL_API.ciMean(est, sig, n, lvl); steps.innerHTML = '
Results
Margin = ' + TOOL_API.zstar(lvl) + ' \u00d7 ' + sig + '/\u221a' + n + ' = ' + r4(r.margin) + '.
'; res.innerHTML = '
' + lvl + '% CI
(' + r4(r.lo) + ', ' + r4(r.hi) + ')
' + '
Margin of error
' + r4(r.margin) + '
'; }); document.getElementById('zGo').addEventListener('click', function(){ var x = num('zX'), m0 = num('zM'), s = num('zS'), n = Math.round(num('zN')); var res = document.getElementById('zResult'), steps = document.getElementById('zSteps'); res.style.display = 'block'; if (n < 2 || s <= 0){ res.innerHTML = '
Need n \u2265 2 and \u03c3 > 0.
'; return; } var r = TOOL_API.ztest(x, m0, s, n); steps.innerHTML = '
Results
z = (' + x + '\u2212' + m0 + ')/(' + s + '/\u221a' + n + ').
'; res.innerHTML = '
z-statistic
' + r4(r.z) + '
' + '
Two-sided p-value
' + r4(r.pTwo) + '
' + '
One-sided (left / right)
' + r4(r.pLeft) + ' / ' + r4(r.pRight) + '
'; }); })();