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Table Of Contents
Python Data Analysis - Fourth Edition
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Missing values refers to the absence of data in a dataset in which the specific dataset variables and observations do not contain any value. They differ from the case where the value is not in a consistent format; missing values mean no values are recorded at all.
For instance, in a survey questionnaire, there could be an optional question such as “You can choose not to answer the question: ‘How old are you?’”. For respondents who decline to answer the question, the data corresponding to this variable will be treated as missing.
The next question is: Why do we need to care about missing values for the validity of our data analysis? There are a few reasons why missing data could have an impact: