Paste numbers to calculate Q1, median, Q3, interquartile range, and 1.5×IQR fences.
Calculate Q1, median, Q3 and IQR with selectable quartile methods, Tukey fences, outliers and a box-plot verification view.
Use descriptive context first, choose the method that matches the design, then keep inputs, settings and result evidence reproducible instead of copying a p-value without its analysis recipe.
Use plots and descriptive summaries before formal tests. Check the sampling/design assumptions that matter for the chosen method, report effect size and uncertainty where available, and avoid treating a threshold such as p < .05 as proof of importance, causation, or truth. Browser calculations are educational/planning utilities, not domain-specific professional advice.
Use the tool first, then use these checks to interpret, verify and hand off the result without displacing the primary workflow.
Quartile software does not always use the same rule for small or even-sized samples. Record whether you used interpolation or Tukey-style halves, then compare Q1 and Q3 under the same method before treating a difference as a data problem. If a class, spreadsheet, or statistics package specifies a convention, match that convention rather than mixing methods between steps.
After the tool reports Q1, Q3, and IQR, independently compute IQR = Q3 − Q1 and then the lower and upper fences from the selected multiplier. Check a short sorted dataset by hand. This catches transcription mistakes and also makes it clear that the usual 1.5× IQR rule flags potential outliers; it does not prove that a value is erroneous.
A box plot is useful for center, spread, skew hints, and flagged points, but it hides repeated values and local clusters. Keep the original observations available when the decision depends on sample size, multimodality, measurement limits, or whether an extreme point has a plausible real-world explanation.
Removing missing entries, parsing commas, rounding measurements, or excluding a flagged point can change quartiles. When comparing two versions or groups, keep the same cleaning rule and report the number of observations alongside the IQR. A reproducible preprocessing rule is more useful than silently editing the list until the box plot looks cleaner.
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