2. Are There Any Outliers? Using the 1.5*IQR Rule

3. Say we have the following data: 1,2,5,5,7,8,10,11,11,12,15,20 Notice that you must have ordered data before you can find the Five – Number – Summaries. Find the median first. It’s the middle point. Then find the quartiles, Q 1 and Q 3. They are the middles of the lower and upper half, respectively. The last thing to do is determine whether there are outliers using the 1.5*IQR Rule

4. min Q 1 Q 3 max 1,2,5,5,7,8,10,11,12,12,18,25 9512 IQR = 12 – 5 = 7 22.5 1.5IQR -5.5 11825 25 is considered an outlier and will be a point in a boxplot and the ‘whisker’ ends at the last non-outlier data point. 12 + 1.5 * 7 = 22.55 - 1.5 * 7 = -5.5