Exam 2- Influential Observations

Question 0

In regression not all influential points have ….. Residuals

Answer 0

Large

Or influential points may have small residuals

Question 1

Influential observation

Answer 1

An outlier in either the x or y direction which, if removed, would markedly change the value of the slope and y-intercept

Question 2

In regression outliers are often but … Influential

Answer 2

Not always

Or not all outliers are influential

Question 3

In regression the outliers in … Direction are often influential

Answer 3

X

Question 4

Extrapolation

Answer 4

Predicting for an X value outside the range of observed X values used to obtain the line

Question 5

Association (correlation r) between explanatory variable x and response variable y , even if strong does not imply ….

Answer 5

Causation

Question 6

Drawbacks of observational studies

Answer 6

1. Cannot systematically change x and observe change in Y
2. Cannot randomize
3. Cannot conclude causation

Question 7

To get good evidence of causation do an

Answer 7

Experiment

Question 8

Supporting causation without experimentation

Answer 8

Smoking and lung cancer -

• strong association
• association consistent across studies
• alleged cause is plausible