Stat: 怎能知道reject or accept H0

i wanna to know how can i recongize reject or accpet H0...

For example: 我計左個數 and compare with the t-table 果個數...is it accept H0 if my calcuable value is greater than the t-table value...

不過有時個數係負數,,,,咁我又唔知點啦...can someone explain to me about this