Day 56 Identifying Outliers

Introduction In some data, some points appear not to be inaccurately recorded due to their difference from others. These may be too large or too small as compared to other values. We would like to be able to identify these points in a graph and also in a table if possible.

Vocabulary: Outliers The are points that do not follow the general trend of other points in a given data. This can be done in the notebooks or on vocabulary cards. Whatever system you use 

Outliers These are points that do not follow the trend of others in a given data. They may be too large or too small compared to other data points. They are worth noting because sometimes, they may affect the characteristics of data such as mean and standard deviation among others.

Example 1 In the scatter plot below, the outlier is the point that is the highest among others. As such, it does not conform to the general trend of the other points. It is enclosed in a blue circular line.

Example 2 In the graph below, the outlier is the point that is very far from the others. It is enclosed in blue circular line.

Example 3 In the figure below, the outlier is the point that is at the lowest point as compared too other points. Thus, it is the smallest one among the others points. It is enclosed in a blue circular line.

Example 4 The graph below does not have an outlier since all points lie along the general trend of the others.

Identifying outliers from tables Sometimes, it is not easy to identify an outlier from a table, however, in simple tables where it is clear what the highest or lowest point is, an outlier would be the one that seems to be outside the general trend of other points. Example 5 Identify an outlier from the following tables (i). 1 2 3 4 5 6 7 8 9 24 11 13 15

(ii). From table (i), the outlier is the highest point as compared to the general trend of others. Thus, the outlier is 5, 24. From table (ii), the outlier is the lowest point as compared to the general trend of others. Thus, the outlier is 1,1. 1 2 3 4 5 6 7 8 15 17 16 18 19 21 23

homework A teacher would like to establish the mean age of students in grade 8. He samples out 12 students and record their age as shown below. 13, 13, 13.5, 13.5,14, 14, 14, 14.5,14.5,14.5, 15, 19. a). Draw a scatter plot showing the data above. b).Identify the outlier

Answers homework a). b). The outlier is 19 years

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