1 / 16

Chapter 8 (3-4), 9

Chapter 8 (3-4), 9. More about Correlation. Today’s Lecture. SD Line Calculating r correlation vs causation. The SD Line. the line the points cluster around passes through the point of averages: (AVGx , AVG Y ) Has slope : . Calculating r (call variables “X” and “Y”).

zinna
Download Presentation

Chapter 8 (3-4), 9

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 8 (3-4), 9 More about Correlation

  2. Today’s Lecture • SD Line • Calculating r • correlation vs causation

  3. The SD Line • the line the points cluster around • passes through the point of averages: (AVGx , AVGY) • Has slope :

  4. Calculating r(call variables “X” and “Y”) • Step 1: Calculate AVGx and AVGy • Step 2: Calculate SDx and SDy • Step 3: Standardize each variable • Step 4: Find average of products of z-scores (standard scores)

  5. NOTE: The Correlation Coefficient is unaffected if the units of measurement are changed Example: Correlation between height and weight remains the same whether height is measured in inches, cm., feet, etc.

  6. Important Note: Correlation DOES NOT Imply Causation • strong association between 2 variables is not enough to justify conclusions about cause and effect

  7. Examples Strong association between: • number of firefighters and amount of damage • Does sending more firefighters cause more damage? • shoe size and score on a reading comprehension exam for elementary school children • What’s the explanation? • SAT and GPA scores • What’s the explanation?

  8. Important Note: Correlation DOES NOT Imply Causation • strong association between 2 variables is not enough to justify conclusions about cause and effect • best way to get evidence that X causes Y is through a controlled experiment

More Related