A night class has Q1 = 78, Q3 = 89 and an interquartile range of 11. Below what test score is a value treated as an outlier?

1. The lower fence is the first quartile minus 1.5 times the interquartile range. 2. One and a half times 11 marks is 16.5 marks. 3. Subtracting 16.5 from 78 gives a lower fence of 61.5 marks. 4. Any score under 61.5 marks is therefore an outlier, which catches the scores of 45 and 25.5. 5. A cut at 67.0 marks would follow from subtracting only one interquartile range instead of one and a half. 6. A cut at 78.0 marks is the quartile itself and would label a quarter of the class as outliers. _Source: OpenStax Introductory Business Statistics (CC BY 4.0), Ch 2 "Descriptive Statistics", section 2.2 Measures of the Location of the Data_