topic Test for significant difference in proportion of Males from 2005 to 2010 in Statistical Procedures

Test for significant difference in proportion of Males from 2005 to 2010

HyunJee — Thu, 17 May 2012 17:19:05 GMT

I am trying to determine if the proportion of Males over the time period of 2005 to 2010 changes significantly. Below is a breakdown of the proportions of gender over the years time period. I am having issues determining the best process to use to conclude if there is a significant change over time in the proportion of Males for my study. Thank you for any help you can provide.

I FIRST CREATED A DATASET FROM THE PROC FREQ OUTPUT

proc freq data=demographics;

tables gender/out=gender noprint;

by year;

run;

PERFORM A TTEST TO DETERMINE IF YEAR PROPORTIONS OF MALES DIFFER - IS THIS CORRECT?

proc ttest data=gender;

var percent;

where gender = "M";

run;

PERFORM A GLM MODELING YEAR AS MY OUTCOME - IS THIS CORRECT?

proc glm data=gender;

model year=percent;

where gender = "M";

run;

year	Gender	Frequency	Percent of Total
year	Gender	Count	Frequency
2005	F	17248	48.6902
2005	M	18176	51.3098
2006	F	16791	49.2968
2006	M	17270	50.7032
2007	F	17027	49.6356
2007	M	17277	50.3644
2008	F	17480	49.3409
2008	M	17947	50.6591
2009	F	19291	49.2733
2009	M	19860	50.7267
2010	F	22624	49.2619
2010	M	23302	50.7381

Re: Test for significant difference in proportion of Males from 2005 to 2010

Doc_Duke — Thu, 17 May 2012 18:08:45 GMT

Neither of the approaches that you showed are correct because they don't take the sample size into account. There are several ways to approach this.

you could simply do a trend test in the PROC FREQ. Add the TREND option to the TABLES statement. This assumes that year is ordinal scale.
you could do a logistic regression with gender as the outcome and year as the predictor. This assumes that year has a ratio scale.

Doc Muhlbaier

Duke

Re: Test for significant difference in proportion of Males from 2005 to 2010

HyunJee — Thu, 17 May 2012 18:36:16 GMT

Thank you for your suggestions. I do realize now that I was not taking into account sample sizes.

I ran the suggested analysis and they do tell me if the proportions of gender change over time. Thank you again.

Re: Test for significant difference in proportion of Males from 2005 to 2010

Doc_Duke — Fri, 18 May 2012 16:26:49 GMT

You are welcome. One caution is in interpretation. You have a very large sample size, so the test may be statistically significant without being "important". You observed a 0.6% drop between 2005 and 2006 and no more than a 0.25% after that; which may or may not be "important" depending on the context.