Community Trekker

Joined:

Apr 9, 2014

## Regression Analysis

Hello Everyne.

One new question: I have a regression line (please see attachment)  Y xs X.

I have calculated the confidence intervals for Y as a function or X.

However based on this fit, when I want to get the confidence intervals of X how do I calculate them.

The reason for this question is that ofter times we obsere a response (Y) and then read back the X value from the regression line. Therefore when an X value is read out of this regression line, it should theoretically also have a confidence interval ?

I am much obliged for your kind assistance.

1 ACCEPTED SOLUTION

Accepted Solutions

Staff

Joined:

Jun 23, 2011

Solution

## Re: Regression Analysis

This is known as inverse prediction or the calibration problem. You have a standard curve and correctly fit Y (response) versus X (known levels). This result is available but not in the Bivariate platform that you used. Use the Fit Least Squares platform instead. Select Analyze > Fit Model. Enter your Y column in the Y role, enter your X column as an Effect, and click Run. Click the red triangle at the top and select Estimates > Inverse Prediction. Choose your confidence level and your desired type of interval. Enter up to eight Y values. Finally, use the option at the bottom to indicate if you want an interval estimate for the mean X (default) or the individual X value (check the box).

Learn it once, use it forever!
5 REPLIES

Super User

Joined:

Jun 22, 2012

## Re: Regression Analysis

You can get the confidence interval for your X variable by running the Distribution Platform.

See Mark's response below

Jim

Community Trekker

Joined:

Apr 9, 2014

## Re: Regression Analysis

Hi there,

You mean distribution  X as Y   (right) ?

But this is not very helpful, it generates no meaningful report.  I would be obliged for your assistance .

Staff

Joined:

Jun 23, 2011

Solution

## Re: Regression Analysis

This is known as inverse prediction or the calibration problem. You have a standard curve and correctly fit Y (response) versus X (known levels). This result is available but not in the Bivariate platform that you used. Use the Fit Least Squares platform instead. Select Analyze > Fit Model. Enter your Y column in the Y role, enter your X column as an Effect, and click Run. Click the red triangle at the top and select Estimates > Inverse Prediction. Choose your confidence level and your desired type of interval. Enter up to eight Y values. Finally, use the option at the bottom to indicate if you want an interval estimate for the mean X (default) or the individual X value (check the box).

Learn it once, use it forever!

Community Trekker

Joined:

Apr 9, 2014

## Re: Regression Analysis

This result is available but not in the Bivariate platform that you used.

Use the Fit Least Squares platform instead.

Sorry, could not find this platform ?

Super User

Joined:

Jun 22, 2012

## Re: Regression Analysis

The platform that Mark is referring to is:

Analyze==>Fit Model

Within it you can choose the Least Squares

Jim