Turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

Options

- RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

☑ This topic is **solved**.
Need further help from the community? Please
sign in and ask a **new** question.

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Posted 10-30-2023 10:55 PM
(991 views)

I want to answer the following questions:

- are the lines coincident?
- are the slopes different?
- are the intercepts different?

For that, I have used the following piece of code:

**PROC** **REG** DATA=ALL;

MODEL Y = X Z1 Z2 XZ1 XZ2 Z1Z2;

INTERCEP: TEST Z1, Z2;

SLOPE: TEST XZ1, XZ2;

COINCID: TEST Z1, Z2, XZ1, XZ2;

**RUN**;

How can I interpret the results?

Comments will be deeply appreciated...

Best,

Santiago

1 ACCEPTED SOLUTION

Accepted Solutions

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Sometimes a picture is worth a lot of tests:

proc sgplot data=have; reg x=x y=y/group=z1; run;

Or set ods graphics one and use the PLOTS statement of Proc Reg or Proc GLm or ...

7 REPLIES 7

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

More explanation is needed.

What are the variables X Z1 Z2 XZ1 XZ2 Z1Z2?

--

Paige Miller

Paige Miller

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

X is a continuous explanatory variable; Y is a continuous dependent variable, Z1 and Z2 are dichotomous variables. An example of the data is:

Y | X | Z1 | Z2 |

0.38448 | 11134.94 | 1 | 0 |

0.42872 | 10280.34 | 1 | 0 |

0.45391 | 12595.40 | 1 | 0 |

0.26954 | 7461.27 | 1 | 0 |

0.49276 | 13352.59 | 1 | 0 |

1.09706 | 33692.40 | 1 | 0 |

0.31529 | 8987.04 | 1 | 0 |

0.20629 | 5190.80 | 1 | 0 |

0.49011 | 15962.34 | 1 | 0 |

0.23585 | 6454.96 | 1 | 0 |

0.54901 | 14717.25 | 1 | 0 |

0.26269 | 7757.72 | 1 | 0 |

0.62173 | 14394.44 | 1 | 0 |

0.60383 | 18041.02 | 1 | 0 |

0.47756 | 13406.98 | 1 | 0 |

0.44168 | 11272.19 | 1 | 0 |

0.09205 | 2349.10 | 1 | 0 |

0.32221 | 8780.78 | 1 | 0 |

0.19188 | 5586.24 | 1 | 0 |

0.19467 | 4797.40 | 1 | 0 |

0.08793 | 2121.80 | 1 | 0 |

0.13247 | 3744.60 | 1 | 0 |

0.22353 | 5683.04 | 1 | 0 |

0.09343 | 2175.01 | 1 | 0 |

0.47902 | 13764.63 | 0 | 1 |

0.21821 | 5703.75 | 0 | 1 |

0.08321 | 1954.22 | 0 | 1 |

0.15906 | 4490.16 | 0 | 1 |

0.50418 | 15138.00 | 0 | 1 |

0.08847 | 2178.00 | 0 | 1 |

0.16686 | 4471.20 | 0 | 1 |

0.17571 | 4435.76 | 0 | 1 |

0.27287 | 7337.30 | 0 | 1 |

0.05631 | 1362.18 | 0 | 1 |

0.13135 | 3717.12 | 0 | 1 |

0.41391 | 11741.91 | 0 | 1 |

0.13025 | 3207.24 | 0 | 1 |

0.34055 | 10097.38 | 0 | 1 |

0.32904 | 8126.60 | 0 | 1 |

0.47509 | 12354.75 | 0 | 1 |

0.80383 | 23064.00 | 0 | 1 |

0.66650 | 18758.08 | 0 | 1 |

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Sometimes a picture is worth a lot of tests:

proc sgplot data=have; reg x=x y=y/group=z1; run;

Or set ods graphics one and use the PLOTS statement of Proc Reg or Proc GLm or ...

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

I'm surprised you don't get an error from PROC REG since Z1 and Z2 are perfectly correlated. But I really don't use PROC REG much any more.

I would do this in PROC GLM (in which case Z2 is not needed)

```
proc glm data=have;
class z1;
model y=x z1 x*z1;
run; quit;
```

If the statistical test of the effect of Z1 is statistically significant then the intercepts are different. If the effect of X*Z1 is significant, then the slopes are different. I might want to think about this a little more, but if the tests for both Z1 and X*Z1 are both not significant, then the lines are coincident (except for random noise).

--

Paige Miller

Paige Miller

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Thanks so much, ladies and gentlemen...your support is deeply appreciated!!!!

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Thanks so much for your support...

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

So in your original problem statement, you were performing statistical testing in PROC REG. Then you mark correct the answer which just draws plots. I don't think plots is the correct answer, although it may be very helpful to have a plot, there is no statistical testing going on.

--

Paige Miller

Paige Miller

Are you ready for the spotlight? We're accepting content ideas for **SAS Innovate 2025** to be held May 6-9 in Orlando, FL. The call is **open **until September 25. Read more here about **why** you should contribute and **what is in it** for you!

Upcoming Events

- Maximize Efficiency for Data Engineers | SAS Viya August and September Release | 15-Oct-2024
- SAS Bowl XLIV, Model Cards | 16-Oct-2024
- Ask the Expert: Fostering Trustworthy AI Using a Model Card | 17-Oct-2024
- MSUG Presents: | 17-Oct-2024
- BASUG SAS Blowout (In Person) | 18-Oct-2024
- PhilaSUG Onsite Meeting 2024 | 22-Oct-2024
- Ask the Expert: How Do I Clean My Data Using SAS Programming: Part 2 | 22-Oct-2024

Mastering the WHERE Clause in PROC SQL

SAS' Charu Shankar shares her PROC SQL expertise by showing you how to master the WHERE clause using real winter weather data.

Find more tutorials on the SAS Users YouTube channel.