find the missing probability?
x 1 2 3 4
P(X) 0.30 0.40 0.15 ?

Question

find the missing probability?
x       1         2        3        4
P(X)   0.30    0.40  0.15     ?

jim_thompson5910 · Answer

Hint: in any valid probability distribution, all the probabilities must add to 1

anonymous · Answer

soo that means???

jim_thompson5910 · Answer

0.3 + 0.4 + 0.15 + x = 1

solve for x

anonymous · Answer

idk what x is lol thats why i put it on here.
i cant miss this one or i fail. sorry im not good with thid

jim_thompson5910 · Answer

x is unknown and you don't know it until you solve for it

jim_thompson5910 · Answer

0.3 + 0.4 + 0.15 + x = 1

0.85 + x = 1

x = 1 - 0.85

x = ???

jim_thompson5910 · Answer

if we knew what x was, then there would be no need to ask the original question

anonymous · Answer

do i just minus 1 from 0.85?

jim_thompson5910 · Answer

yes

jim_thompson5910 · Answer

1 - 0.85 = ???

anonymous · Answer

i got 0.15

jim_thompson5910 · Answer

same here

anonymous · Answer

so is that right?

jim_thompson5910 · Answer

yes, that's the missing probability

anonymous · Answer

thank you

jim_thompson5910 · Answer

basically you have 4 different possibilities

possibility A has a 30% chance
possibility B has a 40% chance
possibility C has a 15% chance
possibility D has a 15% chance (you just found this one)

They add to 100% and there are no other possibilities

jim_thompson5910 · Answer

and they must add to 100% if these are the only 4 possibilities