a lab network consisting of 20 computers was attack by a computer virus. this virus enters each computer with probability 0.4 independent of others. find the probability that it enters atleast 10 computers? its answer is 0.2447 but i dont know which distribution i should use ?

Question

cwrw238 · Answer

i think you can use the Binomial Distribution

anonymous · Answer

but i gives 0.1171

cwrw238 · Answer

oh - i'm pretty rusty at this stuff - did you use Binomial tables?

anonymous · Answer

nope

anonymous · Answer

ok let me see the table

cwrw238 · Answer

i'll see if i can dig mine out

anonymous · Answer

its of no use

anonymous · Answer

the table is giving .8725

cwrw238 · Answer

P(X>=10) = 1 -P(X<=9) 
                = 1 - F(9;20,0.4)

cwrw238 · Answer

i cant find my tables i'm afraid

anonymous · Answer

np

anonymous · Answer

@cwrw238  can you give the half solution i m again confused plz

cwrw238 · Answer

ah - the tables are online
P = 1 - 0.755 = 0.245 according to them

anonymous · Answer

actually the thing is that i m noob to probability

cwrw238 · Answer

i used the cumulative binomial table

anonymous · Answer

so thanks alot for your help

cwrw238 · Answer

yw - i'm not great at probability - don;t like it very much

anonymous · Answer

@cwrw238 tell me how i can improve my probability

cwrw238 · Answer

i'm sorry i cant really help you there - i expect one of the legends, senseis or gurus should be able to help

anonymous · Answer

You can use the Standard Model Equation...