Dealing with Missing Data

From PsychWiki - A Collaborative Psychology Wiki

(Difference between revisions)
Jump to: navigation, search
Afrjb (Talk | contribs)
m (changed type o / grammar error, the word other was changed to order)
 
(One intermediate revision not shown)
Line 4: Line 4:
*#<u>Listwise deletion</u> – SPSS will not include cases (subjects) that have missing values on the variable(s) under analysis. If you are only analyzing one variable, then listwise deletion is simply analyzing the existing data. If you are analyzing multiple variables, then listwise deletion removes cases (subjects) if there is a missing value on any of the variables. The disadvantage is a loss of data because you are removing all data from subjects who may have answered some of the questions, but not others (e.g., the missing data).  
*#<u>Listwise deletion</u> – SPSS will not include cases (subjects) that have missing values on the variable(s) under analysis. If you are only analyzing one variable, then listwise deletion is simply analyzing the existing data. If you are analyzing multiple variables, then listwise deletion removes cases (subjects) if there is a missing value on any of the variables. The disadvantage is a loss of data because you are removing all data from subjects who may have answered some of the questions, but not others (e.g., the missing data).  
*#<u>Pairwise deletion</u> – SPSS will include all available data. Unlike listwise deletion which removes cases (subjects) that have missing values on any of the variables under analysis, pairwise deletion only removes the specific missing values from the analysis (not the entire case). In other words, all available data is included. [[Image:Fe40.png]] - If you are conducting a correlation on multiple variables, then SPSS will conduct the bivariate correlation between all available data points, and ignore only those missing values if they exist on some variables. In this case, pairwise deletion will result in different sample sizes for each correlation. Pairwise deletion is useful when sample size is small or missing values are large because there are not many values to begin with, so why omit even more with listwise deletion.
*#<u>Pairwise deletion</u> – SPSS will include all available data. Unlike listwise deletion which removes cases (subjects) that have missing values on any of the variables under analysis, pairwise deletion only removes the specific missing values from the analysis (not the entire case). In other words, all available data is included. [[Image:Fe40.png]] - If you are conducting a correlation on multiple variables, then SPSS will conduct the bivariate correlation between all available data points, and ignore only those missing values if they exist on some variables. In this case, pairwise deletion will result in different sample sizes for each correlation. Pairwise deletion is useful when sample size is small or missing values are large because there are not many values to begin with, so why omit even more with listwise deletion.
-
*#In other to better understand how listwise deletion versus pairwise deletion influences your results, try conducting the same test using both deletion methods. Does the outcome change? Also, its important to keep in mind that for each type of test you conduct, you need to identify if SPSS is using listwise or pairwise deletion. Most tests allow you to elect your preference, but you should always check your output for the number of cases used in each analysis to identify if pairwise or listwise deletion was used.
+
*#In order to better understand how listwise deletion versus pairwise deletion influences your results, try conducting the same test using both deletion methods. Does the outcome change? Also, its important to keep in mind that for each type of test you conduct, you need to identify if SPSS is using listwise or pairwise deletion. Most tests allow you to elect your preference, but you should always check your output for the number of cases used in each analysis to identify if pairwise or listwise deletion was used.
Line 17: Line 17:
----
----
-
◄ Back to [[Research_Tools |Research Tools mainpage]]
+
◄ Back to [[Analyzing Data]] page

Latest revision as of 21:13, 11 September 2009

How do I deal with missing values? You have three basic options when dealing with missing values.






◄ Back to Analyzing Data page

Personal tools
Namespaces
Variants
Actions
Navigation
Interaction
Toolbox