Vmstat VS PS comparision not match --need help in urgent AIX

Hi I have a AIX box,

People seatting and looking out for the vmstat and PS CPU % use there .

Problem is that : they used vmstat and looked for the cpu clolumn
which basically have column like cs us sy id
110 1 4 95

After that they looked for ps -a which give the %CPU utilization also

we are in a total confusion as why sum of all the %cpu utilization shown in ps -a and the total sum of vmstat is not same ??

Any help will greatly appriciate as all the Adimin are seatting and discussuing

Hi,
go through man pages of VMSTAT and PS.
~PG