Summary
Summary Research Methods - Data Analysis I
- Course
- Institution
Summary of 2 pages for the course Research Methods In Psychology at UT
[Show more]
Seller
Followkayleighdebruin1
Reviews received
Content preview
RM | Unit 240 - Assumptions part IBook: Analysing data using linear models
Chapter 7: 7.1, 7.2 7.3, 7.4, 7.5
Chapter 7.1: Introduction
For a linear model to be a good model, there are four conditions that need to be fulfilled.
1. linearity The relationship between the variables can be described by a linear equation (also called
additivity)
2. independence The residuals are independent of each other
3. equal variance The residuals have equal variance (also called homoskedasticity)
4. normality The distribution of the residuals is normal
If these conditions (often called assumptions) are not met, the inference with the computed
standard error is invalid. That is, if the assumptions are not met, the standard error should not be trusted,
or should be computed using alternative methods.
Chapter 7.2: Independence
This systematic order in the residuals is a violation of independence: the residuals should be random.
Chapter 7.3: Linearity
The assumption of linearity is often also referred to as the assumption of additivity. Contrary to intuition,
the assumption is not that the relationship between variables should be linear. The assumption is that there
is linearity or additivity in the parameters. That is, the effects of the variables in the model should add up.
the relationship between two variables need not be linear in order for a linear model to be
appropriate. A transformation of an independent variable, such as taking a square, can result in normally
randomly scattered residuals. The linearity assumption is that the effects of a number of variables
(transformed or untransformed) add up and lead to a model with normally and independently, randomly
scattered residuals.
Chapter 7.4: Equal variances
The equal variance assumption is an important one: if the data show that the variance is different for
different subgroups of individuals in the data set, then the standard errors of the regression
coefficients cannot be trusted. → The equal variance assumption is often referred to as the
homogeneity of variance assumption or homoscedasticity. It is the assumption that variance is
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller kayleighdebruin1. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.44. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
76462 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now