Hello!

Can someone help me understand how to go about answering these questions for binomial distributions?

n=8, p=0.2

Find P(X=3)

Find P(X≤3)

Find P(X>4)

Find P(X<5)

Find P(X≥3)

Find P(3

I know these are alot of questions but I missed this lesson because of an illness and have a test to write tomorrow and have zero information on how to answer/do them.

Any help would be very much appreciated! Thank you!

saarad0
Oct 29, 2017

#1**+3 **

Not an expert on these....but I believe that we have :

8 = number of trials p = probability of success on any trial = .2

probability of failure on one trial = 1 - .2 = .8

P(3) = means "probability of 3 successes in 8 trials " =

C(8,3) (.2)^3 (1 - .2)^(8-3) = C(8,3) (.2)^3 (.8)^5 ≈ 14.68%

P (≤3 ) = means probability of 0 successes in 8 trials + probability of 1 success in 8 trials + probability of 2 successes in 8 trials + probability of 3 success in 8 trials =

C (8,0) (.2)^0 (.8)^8 + C (8,1) (.2)^1 (.8)^7 + C (8,2) (.2)^2 (.8)^6 + C (8,3) (.2)^3 (.8)^5 ≈

94.37%

P ( > 4) =

C (8,5) (.2)^5 (.8)^3 + C (8,6) (.2)^6 (.8)^2 + C (8,7) (.2)^7 (.8)^1 + C (8,8) (.2)^8 (.8)^0 ≈

1.04%

Based on this....Can you do the rest ???...if not....let me know....

Here's some more info : http://www.mathwords.com/b/binomial_probability_formula.htm

Note also : P(> 4) = 1 - P( ≤ 4 )

CPhill
Oct 29, 2017