Summary of Discovering statistics using IBM SPSS statistics by Andy Field - 5th edition
- 2856 reads
Join with a free account for more service, or become a member for full access to exclusives and extra support of WorldSupporter >>
Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 13
Covariates are characteristics of the participants in an experiment. These are characteristics outside of the actual treatment. If a researcher wants to compare means of multiple groups using the additional predictors, the covariates, then the ANCOVA is used. Examples of covariates could be love for puppies, softness of puppy fur.
Covariates can be included in an ANOVA for two reasons:
- Reduce within-group error variance
The unexplained variance is attributed to other variables, the covariates, which reduces the total error variance. This allows for a more sensitive test for the difference of group means. - Elimination of confounds
By adding other variables, covariates, in the analysis, confounds are eliminated.
If there are covariates, the b-values represent the differences between the means of each group and the control adjusted for the covariate.
ASSUMPTIONS AND ISSUES WITH ANCOVA
There are two new assumptions for ANCOVA that are not present with ANOVA. These assumptions are independence of the covariate and treatment effect and homogeneity of regression slopes.
The ideal case is that the covariate is independent from the treatment effect. If the covariate is not independent from the treatment effect, then the covariate will reduce the experimental effect because it explains some of the variance that would otherwise be applicable to the experiment. The ANCOVA does not control for or balance out the differences caused by the covariate. The problem of covariates potentially explaining a bit of the data and wanting to filter these confounds is using randomizing participants to experimental groups or matching experimental groups on a covariate.
Another assumption of the ANCOVA is that the relationship between covariate and outcome variable holds true for all groups of participants and not only for a few groups of participants (e.g. for both males and females and not only males). This assumption can be checked by checking the regression line for all the covariates and all the conditions. The lines should be similar.
In order to test the assumption of homogeneity of regression slopes, the ANCOVA model should be customized on SPSS to look at the independent variable x the covariate interaction.
CALCULATING THE EFFECT SIZE
The partial eta squared is the effect size which takes the covariates into account. It uses the proportion of variance that a variable explains that is not explained by other variables in the analysis. It uses the following formula:
Access:
Public
This content is related to:
Summary of Discovering statistics using IBM SPSS statistics by Andy Field - 5th edition
Scientific & Statistical Reasoning – Summary interim exam 2 (UNIVERSITY OF AMSTERDAM)
Check more of this topic?
This content is used in:
Scientific & Statistical Reasoning – Summary interim exam 2 (UNIVERSITY OF AMSTERDAM)
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 12
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 13
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 14
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 15
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 16
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 17
- Dienes (2008). Understanding psychology as a science.” – Article summary
- “Meltzoff & Cooper (2018). Critical thinking about research: Psychology and related fields.” - Article summary
- “Simmons, Nelson, & Simonsohn (2011). False-positive psychology: Undisclosed flexibility in data collection and analysis allows presenting anything as significant.” - Article summary
- “Nosek, Spies, & Motyl (2012). Scientific utopia: II. Restructuring incentives and practices to promote truth over publishability.” - Article summary
Summary of Discovering statistics using IBM SPSS statistics by Andy Field - 5th edition
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 1
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 2
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 3
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 5
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 6
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 7
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 8
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 9
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 10
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 11
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 12
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 13
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 14
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 15
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 16
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 17
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 18
- Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition – Summary chapter 19
Search other summaries?
This content is also used in .....
Scientific & Statistical Reasoning – Summary interim exam 2 (UNIVERSITY OF AMSTERDAM)
This bundle contains everything you need to know for the fifth interim exam for the course "Scientific & Statistical Reasoning" given at the University of Amsterdam. It contains both articles, book chapters and lectures. It consists of the following materials:
...Summary of Discovering statistics using IBM SPSS statistics by Andy Field - 5th edition
This bundle contains the chapters of the book "Discovering statistics using IBM SPSS statistics by Andy Field, fifth edition". It includes the following chapters:
- 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18.
Work for WorldSupporter
JoHo can really use your help! Check out the various student jobs here that match your studies, improve your competencies, strengthen your CV and contribute to a more tolerant world
Check how to use summaries on WorldSupporter.org
Online access to all summaries, study notes en practice exams
- Check out: Register with JoHo WorldSupporter: starting page (EN)
- Check out: Aanmelden bij JoHo WorldSupporter - startpagina (NL)
How and why would you use WorldSupporter.org for your summaries and study assistance?
- For free use of many of the summaries and study aids provided or collected by your fellow students.
- For free use of many of the lecture and study group notes, exam questions and practice questions.
- For use of all exclusive summaries and study assistance for those who are member with JoHo WorldSupporter with online access
- For compiling your own materials and contributions with relevant study help
- For sharing and finding relevant and interesting summaries, documents, notes, blogs, tips, videos, discussions, activities, recipes, side jobs and more.
Using and finding summaries, study notes en practice exams on JoHo WorldSupporter
There are several ways to navigate the large amount of summaries, study notes en practice exams on JoHo WorldSupporter.
- Use the menu above every page to go to one of the main starting pages
- Starting pages: for some fields of study and some university curricula editors have created (start) magazines where customised selections of summaries are put together to smoothen navigation. When you have found a magazine of your likings, add that page to your favorites so you can easily go to that starting point directly from your profile during future visits. Below you will find some start magazines per field of study
- Use the topics and taxonomy terms
- The topics and taxonomy of the study and working fields gives you insight in the amount of summaries that are tagged by authors on specific subjects. This type of navigation can help find summaries that you could have missed when just using the search tools. Tags are organised per field of study and per study institution. Note: not all content is tagged thoroughly, so when this approach doesn't give the results you were looking for, please check the search tool as back up
- Check or follow your (study) organizations:
- by checking or using your study organizations you are likely to discover all relevant study materials.
- this option is only available trough partner organizations
- Check or follow authors or other WorldSupporters
- by following individual users, authors you are likely to discover more relevant study materials.
- Use the Search tools
- 'Quick & Easy'- not very elegant but the fastest way to find a specific summary of a book or study assistance with a specific course or subject.
- The search tool is also available at the bottom of most pages
Do you want to share your summaries with JoHo WorldSupporter and its visitors?
- Check out: Why and how to add a WorldSupporter contributions
- JoHo members: JoHo WorldSupporter members can share content directly and have access to all content: Join JoHo and become a JoHo member
- Non-members: When you are not a member you do not have full access, but if you want to share your own content with others you can fill out the contact form
Quicklinks to fields of study for summaries and study assistance
Field of study
- All studies for summaries, study assistance and working fields
- Communication & Media sciences
- Corporate & Organizational Sciences
- Cultural Studies & Humanities
- Economy & Economical sciences
- Education & Pedagogic Sciences
- Health & Medical Sciences
- IT & Exact sciences
- Law & Justice
- Nature & Environmental Sciences
- Psychology & Behavioral Sciences
- Public Administration & Social Sciences
- Science & Research
- Technical Sciences
1 - left - closed: make a reference to other content or organization:
Comments, Compliments & Kudos:
Add new contribution