How does a restaurant decide how many brussel sprouts portions to prep for any given shift? Prep too many and food gets thrown away, increasing costs. Prepping too many results in increased ticket times, which impacts service. Customers develop a negative impression as their orders are delayed.

Visualizing point-of-sale (POS) data can show historical purchase data to more accurately estimate needs. The box and whisker plot can display the variation in orders during different time periods. The box plot below shows how many brussel sprout portions, whether for a stand-alone order or as a side, were required for the morning and night shifts on each day of week.

Daily portions box and whisker plot for kitchen prep

A box plot provides more than simply looking at averages, which can be skewed by outliers. The bar portion of the graph shows how many portions were needed half the time. The center of the bar (where the color changes) shows the middle (median) portions needed. The bracket shows the top quarter and bottom quarter portion needs. By looking at the middle point and how far the box-and-whisker stretches from the middle, you estimate whether the portions required are more likely to be the lower quantities or the higher ones.

From this example, more of the shifts are bottom heavy. In these cases, it might be best to prep for a quantity around the median value. The Sunday morning shift, however, splits down the middle and covers a wide range. Whether you go with the lower or higher value depends on whether wastage or increased ticket times is of greater concern.

Another bit of information the box plot can provide are outliers. These are the data points that fall outside of the box and whisker. In this plot the Saturday night shift are all outliers, making it difficult to estimate the correct portion to prep. In this case, you might try looking at a plat that includes more POS data.