Table 1. Types of Missing Values.
Types of missing values | Description | Possible causes |
---|---|---|
Missing completely at random | Missing data occur completely at random without being influenced by other data. | Consent withdrawal, omission of major exams, death, discontinued follow-up and serious adverse reactions. |
Missing at random | Missing data occur at a specific time point in conjunction with participant dissatisfaction with study outcomes and ongoing participation | Refusal to continue measurements. |
Not missing at random | Missing data occur when a patient who is not satisfied with study outcomes performs the required measurements on his own, before the scheduled measurement. | If a patient finds the results of self-measurement dissatisfactory in addition to dissatisfaction related to the study, the patient may refuse further measurements. |