topic Re: Mantel test Not significant at strata level BUT significant at aggregated level in Statistical Procedures

Mantel test Not significant at strata level BUT significant at aggregated level

dcortell — Thu, 06 Sep 2018 10:33:46 GMT

I'm running a test where, within a marketing event, for the group of invited people (Attendee VS Not Attendee), I want to test if the N of new opportunity generated has been significatively different between the people attending and people that were invited but not partecipated (a new opportunity could be generated in both groups)

With the following code:

proc freq data=lead_att (where=(outcome_rev2 is not missing) );

tables inter_group*yy_event*outcome_rev3/cmh chisq nocol nopercent trend measures; /*test the trend */

tables inter_group*yy_event*outcome_rev3/cmh nocol nopercent noprint scores=modridit ; /*test existance corr*/


exact mhchi measures trend; 
run;

I get the results below. The Cochran-Mantel Exact Test is significant at aggregated level, by controlling the 'Attending the event' variable, with a values of 4.8065 (Non Zero Correlation).

However, looking at the individual STRATA, the Exact Mantel test is not significant in any of the two strata levels.

How Should I interpret this result? I would expect that as both the strata are not significant, too the aggregated result should follow the same result.

Any suggestion in the interpretation is really appreciated

Re: Mantel test Not significant at strata level BUT significant at aggregated level

Ksharp — Thu, 06 Sep 2018 12:44:33 GMT

It is normal result. No surprise for you .

Re: Mantel test Not significant at strata level BUT significant at aggregated level

dcortell — Thu, 06 Sep 2018 14:45:01 GMT

Hi.

I'm not questioning the result. I'm more questioning how I should interpret it.

It seems to me like , taking into account the individual strata, as the individual Exact Mantel Tests are not significant, then there is not enough evidence to refuse the hypothesis that the share opportunities generated (in %) are equal between each event edition.

But then, If we analyze the aggregated result, then the Exact Mantel test suggest us that indeed exists an association between event edition and share of opportunities generated.

The thing I'm missing is how to connect the two results at a theoretical level

Re: Mantel test Not significant at strata level BUT significant at aggregated level

Ksharp — Fri, 07 Sep 2018 12:56:03 GMT

No connection. You just watch data at two different side.