Turn on suggestions

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

Showing results for

- Home
- /
- Analytics
- /
- Stat Procs
- /
- Question regarding the value of upper 95% CI over 100% generated from ...

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** and **locked**.
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 08-22-2019 10:05 AM
(819 views)

Hi Everyone,

I used Proc CAUSALMED to perform mediation analysis and found some values of Percentage Mediated Wald 95%

Confidence Limits are 100%. Does it make sense?

P.S. I also noticed that SAS PROC also showed similar results. Please see the link below. Page: 2127

Output 33.3.8: **Percentage Due to Interaction **-68.5853 167.6 -397.04 259.87

https://support.sas.com/documentation/onlinedoc/stat/143/causalmed.pdf

Thank you,

Rosy

1 ACCEPTED SOLUTION

Accepted Solutions

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

4 REPLIES 4

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

Good question.

The Wald Confidence Limits reporting a value above 100% is most likely due to high variability in the estimate, like in the documentation example you reference where the standard error estimate is 167.58.

The estimate reported as the percentage due to interaction could be over 100%, but in that case the estimate is not interpretable. This point is touched on in the Counterfactual Framework for Defining Causal Mediation Effects section of the PROC CAUSALMED documentation but can be easy to miss since it involves a bit of notation and a few different equations. I'll provide more detail below, but basically the estimate for the percentage due to interaction might be over 100% if a portion of the four way decomposition of the total effect has the opposite sign of the total effect, and when that occurs the contributions in the decomposition are not interpretable.

Specifically, the four way decomposition of the total effect (TE) says it is equal to the sum of the controlled directed effect (CDE), reference interaction (IRF), mediated interaction (IMD), and pure indirect effect (PIE). The portion attributed to interaction (PAI) is then defined to be PAI=IRF + IMD.

This leads to the three way decomposition, TE = PAI + CDE + PIE. So if the PIE and CDE have the opposite sign than than the TE, then the percentage due to interaction PAI/TE will be over 100%, again in this case it would not be interpreatable.

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

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

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

Super. Many thanks Rick.

Rosy

**Available on demand!**

Missed SAS Innovate Las Vegas? Watch all the action for free! View the keynotes, general sessions and 22 breakouts on demand.

What is ANOVA?

ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.

Find more tutorials on the SAS Users YouTube channel.