Figure 2. Comparison of head extension during laryngoscopy with the three laryngoscopes. These plots show the population statistics, median and quartile values, for head extension angles measured externally with the angle finder in 35 patients for the Macintosh and Miller laryngoscopes and in 27 patients for the Bullard laryngoscope. Outlying points are shown above the columns. Data on the left are for arytenoid exposure, on the right for best view of the larynx. Median values are denoted by white lines across the columns. The 25th and 75th percentile values are represented by the boundaries between the stippled and hatched portions of the columns. The 10th and 90th percentile values are located at the lower and upper ends of the columns, respectively. The Macintosh arytenoid values are labeled as an example, to the left of the column. More than 25% of the patients had 0 degree head extension with the Bullard blade, thus separate 10th percentile values are not shown. The asymmetry of the upper and lower quartile values around the median suggests that head extension angles are not distributed normally, * P < 0.05, Bullard versus other two laryngoscopes.