In another case, still with data from the Brazilian stock market, the stock of the company Magazine Luiza appreciated 30.8% on a day when the stock market index rose by only 0.7%. Still from the graph above you can see that although different from the others, the data is not exactly outside the curve.Ī predictive model could easily infer with high precision that a 9% drop in the stock market index would represent a 15% drop in Petrobras’ share price. The data of the above example may be called outlier, but if taken literally, it can not necessarily be considered a “outlier.” The “curve” in the above graph, although counter-intuitive, is represented by the straight line that cuts the points. In analyzing the chart below, even in the face of several observations, it is easy to identify the point that disagrees with the others. Certainly, the Joesley’ facts strongly affected the average down.
This case represents an outlier for the analyst who, for example, wants to know what was the average daily return on Petrobrás shares in the last 180 days. This strong negative variation had as main motivation the Joesley Batista, one of the most shocking political events that happened in the first half of 2017. Most of the shares of the Brazilian stock exchange saw their price plummet on that day. On Petrobras shares fell 15.8% and the stock market index (IBOVESPA) fell 8.8% in a single day. Sample of 8000 appointments Case: outliers in the Brazilian financial market This is a case, for example, of a given outlier that deserves to be studied, because the behavior of this lady can bring relevant information of measures that can be adopted to increase the rate of attendance in the schedules. However, a curious case was that of an outlier, who at age 79 scheduled a consultation 365 days in advance and actually showed up in her appointment. In the dataset, several patterns have been found, for example: children are practically not missing their appointments and women attend consultations much more than men. In a study already published on Aquarela’s website, we analyzed the factors that lead people no-show in medical appointments scheduled in the public health system of the city of Vitória in the state of Espirito Santo, which caused and approximate loss of 8 million US dollars a year million. Case: outliers in the Brazilian health system Here are some examples that illustrate the view of outliers with graphics. When plotting a chart the analyst can clearly see that something different exists.
One of the best ways to identify outliers data is by using charts. This task becomes even more difficult when many variables (the worksheet columns) are involved. But when the number of observations goes into the thousands or millions, it becomes impossible. In a small sample the task of finding outliers with the use of tables can be easy.
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