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# stats watch

1. the random variable x has a B(40, 0.3) distribution. the mean of a random sample of n observations of x is denoted by x bar

find P(xbar >= 13)

i dont know how to do this because n isnt given

thanks
2. why isn't just 40 X~B(n,p) so n=40? - what answer does the book give anyway
3. (Original post by davidreesjones)
why isn't just 40 X~B(n,p) so n=40? - what answer does the book give anyway
o yeah ops i feel stupid!! but i still get the wrong answer the book says its 0.0084 but thats no where near the answer i get!
4. (Original post by sarah12345)
o yeah ops i feel stupid!! but i still get the wrong answer the book says its 0.0084 but thats no where near the answer i get!
what did u get? There's table for 40, isn't it?
P(X>=13) = 1- P(X<=12). Did u do like that?
5. (Original post by BCHL85)
what did u get? There's table for 40, isn't it?
P(X>=13) = 1- P(X<=12). Did u do like that?
the tables dont go up to 40 so i used a normal approximation but the answer i got was totaly different! grrrrrrrrrr hate stats!

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