{smcl}
{hline}
help for {hi:ttesttable}{right:Version 1.3}
{hline}

{title: Differences in means by groups including the T-test}


{p 4 17 2}{cmd:ttesttable} {it:outcome} {it:groupvar} [if] [in] [,
	{cmdab:uneq:ual}
	{cmdab:tex:(}{it:str}{cmd:)}
	{cmdab:html:(}{it:str}{cmd:)}
	{cmdab:xml:(}{it:str}{cmd:)}
	{cmdab:pre:table(}{it:str}{cmd:)}
	{cmdab:post:table(}{it:str}{cmd:)}
	{cmdab:force}
	{cmdab:r:eference(}{it:str}{cmd:)}
	{cmdab:f:ormat(}{it:{help format:fmt}}{cmd:)}
	{cmdab:texf:ormat(}{it:{help format:fmt}}{cmd:)}
	]



{title:Description}

{p 4 4 4} ttesttable is a very simple Stata module that performs a mean-comparison test (t-Test) 
for all possible combinations of groups defined by a variable. For instance, if you have 4 types 
of observations and you would like to see if there are differences in means between groups, this 
module computes the t-test for all six possible combinations. The output is presented in a table 
of differences in means and includes the significance level of the t-test. This table can be 
exported directly as a LaTeX file and the underlying matrices are available for further use in Stata.

{p 4 4 4} {cmd:outcome} This variable must be numeric and contains the variable you would like to test.  

{p 4 4 4} {cmd:groupvar} This variable must be a categorical variable with either numerical values or strings.


{title:Options}

{p 4 4 4} {cmdab:uneq:ual} This option corresponds to the {it:unequal} option of the command 
{it:ttest}, meaning that no equal variances of the outcome variable are assumed for the two groups. 

{p 4 4 4} {cmdab:tex:(}{it:str}{cmd:)} Use this option to export the displayed table directly 
to latex. Specify the name of the file (without the file extension). The table will be generated 
with the LaTeX {it:tabular} environment. To include the {it:table} environment, use the options 
{cmdab:pre:table(}{it:str}{cmd:)} and {cmdab:post:table(}{it:str}{cmd:)}

{p 4 4 4} {cmdab:html:(}{it:str}{cmd:)} Use this option to export the displayed table in the HTML format. 
The exported file can be opened in any browser (e.g. Firefox, Opera, Internet Explorer, etc). Specify the name 
of the file (without the file extension). Use the option {cmdab:f:ormat(}{it:{help format:fmt}}{cmd:)} 
to format the output. 

{p 4 4 4} {cmdab:xml:(}{it:str}{cmd:)} Use this option to export the displayed table in the XML format, which
can be opened by Excel. Specify the name of the file (without the file extension). Use the option 
{cmdab:f:ormat(}{it:{help format:fmt}}{cmd:)}  to format the output. 

{p 4 4 4} {cmdab:pre:table(}{it:str}{cmd:)} Only for LaTeX export. Include here LaTeX code you would like to have in 
the tex-file before the {it:tabular} environment. This option is only available when the option 
{cmdab:tex:(}{it:str}{cmd:)} is specified.

{p 4 4 4} {cmdab:post:table(}{it:str}{cmd:)} Only for LaTeX export. Include here LaTeX code you would like to have in 
the tex-file after the {it:tabular} environment. This option is only available when the option 
{cmdab:tex:(}{it:str}{cmd:)} is specified.

{p 4 4 4} {cmdab:force} By default, the program stops working when more than 10 categories are 
detected, since this will lead to extremely large tables and is most likely due to the use of a 
continuous variable as grouping variable. If you want to perform the analysis with more than the 
generally admitted 10 categories, use the option force, which eliminates this limit. 

{p 4 4 4} {cmdab:r:eference(}{it:str}{cmd:)} By default, the program computes the full table of all possible combinations.
If you are only interested in the comparison of some values with the remaining, you can use this option. By
indicating with which values you would like to compare. The columns will then be the values you indicate, while the
rows remain the same.  

{p 4 4 4} {cmdab:f:ormat(}{it:{help format:fmt}}{cmd:)} This option allows you to change the format of the display
on the Stata output screen. The default value is %6.3f.

{p 4 4 4} {cmdab:texf:ormat(}{it:{help format:fmt}}{cmd:)} Only for LaTeX export. This option allows you to change the format of the values 
exported to the LaTeX file. Default is: %6.3f

{title:Output}
{p 4 4 15} Besides the screen output and the export to LaTeX, HTML and XML, ttesttable generates three matrices 
which can be accessed through "return list": 

{p 8 4 4} r(p) : matrix of p-values

{p 8 4 4} r(t) : matrix of t statistics

{p 8 4 4} r(diff) : matrix of differences in means


{title:Example}

{p 0 4 0}{cmd:ttesttable} score country, tex(myfile) pre("\begin{table}[!ht]\centering") 
post("\caption{Cross table of differences in mean by group\end{table}"

{p 4 4 15}This example will provide a matrix containing the differences in the average scores 
across countries and performs a T-test for any combination of groups. The stars will indicate 
if the difference is significantly different from zero. The table will be exported to the file 
{it:myfile.tex} and include the {it:table} environment as defined by the options {cmd:pre()} and {cmd:post()}

{p 0 4 0}{stata sysuse auto}

{p 0 4 0}{stata ttesttable price rep78, f(%6.1f) ref(1 2)}

{p 4 4 15}This computed the t-Test according to the group variable {it:rep78} on the outcome variable {it:price}. The option ref(1 2) 
limits the comparisons to the values of 1 and 2 of the variable rep78 with all other values. Additionally, f(%6.1f) changes the format to a one decimal
with 5 leading values for the Stata output.

{title:Acknowledgements}
{p 4 4 1}	I would like to thank Sarah Necker of the suggestion to add the option 'reference' and Rita Maria Ribeiro Bastião for the suggestion to include 
HTML and XML export options. 

{title:Author}
{p 4 4 4}	For suggestions and questions, please contact the author: {break} 
Florian Chávez Juárez: {browse "mailto:florian@chavezjuarez.com?subject=ttesttable:":florian@chavezjuarez.com}

{title:Update}
{browse "http://econ.chavezjuarez.com/vcheck.php?i=ttesttable&v=1.3":Click here to check if you have the newest version}