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Melaniebowman65 · Oct 10, 2007, 09:22 AM

If 20%o of the students performed at top if picked 10 students what is the probablity of EXACTLY 4 of those being a top performers and if you picked 10 students what is the probability of AT LEAST 2 of those students being a top performer and what is the probablity of NO MORE than 2 students being top performers?

eawoodall · Oct 11, 2007, 10:13 PM

the probability of any event, added to it NOT happening is one.
P + -(P) = 1.

20% of the students are top.
1-20%=1-(20/100)=1-(1/5)=5/5 - 1/5 = 4/5= 4/5 * 20/20 = 80%.
80% are NOT top.

if you pick 10 students what is probability of

exactly 4 top students?

at least 2 being top = 1 - (not zero exactly or not one exactly) top students?

2 or less top students?

that sets up how to do it. Here is an example to help more.
ex: how to get exactly 10 top students?
(.2)^10 = (1/5)^10 = 1/9765625

I think if I give more examples I may be doing your homework for you.