Consider the following pairs of variables; what type of a correlation would you expect to find between them:

1. # of hours spent practicing at a golf driving range Vs. your golf drive distance
2. # of hours spent practicing at a golf driving range Vs. your golf score
3. size of a corn harvest & the size of an apple harvest
4. your mark on a geometry test & your mark on an algebra test
5. your income vs. the # of CD’s you purchase

We cannot just assume that because 2 variables have a (strong) positive correlation, that a true relationship genuinely exists and that one affects the other. To perform a complete analysis, you must do 2 things:

1. and then

2.

These are called: _________________________________

5 main types of causal relationships exist:

Let’s consider example 1 on page 196 of your text.

Definition: Extraneous Variables are

Example: consider the variables term marks obtained vs.final exam marks

~ the probable correlation which exists is:

~ possible extraneous variables which exist could be:

To reduce the effect of extraneous variables researches often compare 2 sets of groups: ____________________________________________

Definition:

Definition: A placebo effect occurs when

Example: Quitting smoking research wants to test a drug to see if it helps smokers quit. 50 people who want to quit smoking volunteer. The researcher divides the group equally into moderate/heavy smokers.

Group 1: is given the nicotine patch with the new drug

Group 2: is given a nicotine patch without anything in it.

Results found show that 14 people in Group 1 quit and 9 people in group 2 quit.

a) Which is the experimental group? ________________

b) Which is the control group? ________________

c) What is the independent variable? ________________________

d) What’s the dependent variable? ________________________

e) Can the researcher conclude the new drug is effective?