由于第一次使用stata，还请各位多多指教. 老师给出的分析步骤如下；

Univariate analyses

Please make descriptive statistics (by using ‘tabstat’ command) of pch_asset, pch_ftasset, pch_employee, ch_rdexr, ch_adcostr, dec_dividend, omit_dividend separately for the following samples
A)  All Year 2008 sample firms. Show descriptive statistics for year 2007 and 2008.
B) Year 2008 sample firms that adopt stock option plans at 2006 (so=1). Show descriptive statistics for year 2007 and 2008.
C) Year 2008 sample firms that do not adopt stock option plans at 2006 (so=0). Show descriptive statistics for year 2007 and 2008). (Please conduct mean and median difference tests between samples B) and C). Use ‘ttest’ command and ‘ranksum’ command.)

请教各位，如何编写分析程序？不胜感谢~~！