{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

IPS6eCh02_4bb

# IPS6eCh02_4bb - Looking at Data Relationships IPS Chapter...

This preview shows pages 1–7. Sign up to view the full content.

Looking at Data - Relationships Cautions about Correlation and  Regression IPS Chapter 2.4

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Objectives (IPS Chapter 2.4) Cautions about correlation and regression Residuals Outliers and influential points Lurking variables Correlation/regression using averages The restricted range problem
Correlation/regression using averages Many regression or correlation studies use average data. While this is appropriate, you should know that correlations based on averages are usually quite higher than those made on the raw data. The correlation is a measure of spread (scatter) in a linear relationship. Using averages greatly reduces the scatter. Therefore, r and r 2 are typically greatly increased when averages are used.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Each dot represents an average. The variation among boys per age class is not shown. Should parents be worried if their son does not match the point for his age? If the raw values were used in the correlation instead of the mean, there would be a lot of spread in the y -direction, and thus the correlation would be smaller. Boys These histograms illustrate that each mean represents a distribution of boys of a particular age. Boys
That's why typically growth charts show a range of values (here from 5th to 95th percentiles). This is a more comprehensive way of displaying the same information.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
The distances from each point to the least-squares regression line give us potentially useful information about the contribution of individual data points to the overall pattern of scatter.
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern