# need help with grade 12 data management

• Sep 18th 2006, 01:46 PM
jenneedshelp
need help with grade 12 data management
Hi. I have two questions"

1) Given the following coefficients of correlation, state what percent of variation in y is due to the variation in x.

A) r=0.41 b)r=-0.93 c)r=-1.0

How would I do a question like this?

and...

2) given the chart:

http://img66.imageshack.us/img66/3757/chartft8.png

find the equation of the line of best fit. How did you do this?

*I have no clue how to find the equation. I am so confused.

Thanks in advance for any help, I greatly appreciate it.

Jenn
• Sep 18th 2006, 02:19 PM
JohnM
Quote:

Originally Posted by jenneedshelp
Hi. I have two questions"

1) Given the following coefficients of correlation, state what percent of variation in y is due to the variation in x.

A) r=0.41 b)r=-0.93 c)r=-1.0

How would I do a question like this?

and...

2) given the chart:

http://img66.imageshack.us/img66/3757/chartft8.png

find the equation of the line of best fit. How did you do this?

*I have no clue how to find the equation. I am so confused.

Thanks in advance for any help, I greatly appreciate it.

Jenn

1)
If you square each correlation coefficient, you'll get r^2 - the coefficient of determination, which is the percentage of the variation in y due to the variation in x.

2)
the equation of any linear best fit line is the form y = mx + b where m is the slope and b is the y-intercept (value of y when x=0)

the following link shows you the equations for finding m and b from data - go down approx 1/3 of the page:

Regression: Fitting Functions to Data