statistics Statistics (from German language, German: ''wikt:Statistik#German, Statistik'', "description of a State (polity), state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of ...

, listwise deletion is a method for handling

missing data In statistics, missing data, or missing values, occur when no data value is stored for the variable in an observation. Missing data are a common occurrence and can have a significant effect on the conclusions that can be drawn from the data. Miss ...

. In this method, an entire record is excluded from analysis if any single value is missing.

Example

For example, consider the following questionnaire, as answered by 10 subjects: A researcher is hoping to

model A model is an informative representation of an object, person or system. The term originally denoted the Plan_(drawing), plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a mea ...

income (

dependent variable Dependent and independent variables are variables in mathematical modeling, statistical modeling and experimental sciences. Dependent variables receive this name because, in an experiment, their values are studied under the supposition or demand ...

) based on age and gender (independent variables). Using listwise deletion, the researcher would remove subjects 3, 4, and 8 from the

sample Sample or samples may refer to: Base meaning * Sample (statistics), a subset of a population – complete data set * Sample (signal), a digital discrete sample of a continuous analog signal * Sample (material), a specimen or small quantity of s ...

before performing any further analysis.

Problems with listwise deletion

Listwise deletion affects

statistical power In statistics, the power of a binary hypothesis test is the probability that the test correctly rejects the null hypothesis (H_0) when a specific alternative hypothesis (H_1) is true. It is commonly denoted by 1-\beta, and represents the chances ...

of the tests conducted. Statistical power relies in part on high sample size. Because listwise deletion excludes data with missing values, it reduces the sample which is being statistically analysed. Listwise deletion is also problematic when the reason for missing data may not be random (i.e., questions in

questionnaires A questionnaire is a research instrument that consists of a set of questions (or other types of prompts) for the purpose of gathering information from respondents through survey or statistical study. A research questionnaire is typically a mix of ...

aiming to extract sensitive information. Due to the method, much of the subjects' data will be excluded from analysis, leaving a

bias Bias is a disproportionate weight ''in favor of'' or ''against'' an idea or thing, usually in a way that is closed-minded, prejudicial, or unfair. Biases can be innate or learned. People may develop biases for or against an individual, a group, ...

in data findings. For instance, a questionnaire may include questions about respondents drug use history, current earnings, or sexual persuasions. Many of the subjects in the sample may not answer due to the intrusive nature of the questions, but may answer all other items. Listwise deletion will exclude these respondents from analysis. This may create a bias as participants who do divulge this information may have different characteristics than participants who do not.

Multiple imputation In statistics, imputation is the process of replacing missing data with substituted values. When substituting for a data point, it is known as "unit imputation"; when substituting for a component of a data point, it is known as "item imputation". ...

is an alternate technique for dealing with missing data that attempts to eliminate this bias.

Compared to other methods

While listwise deletion does have its problems, it is preferable to many other methods for handling missing data. In some cases, it may even be the least problematic method. The following table provides some comparisons of listwise deletions to other methods:

References

{{DEFAULTSORT:Listwise Deletion Missing data