# probability

• Dec 9th 2008, 10:17 PM
Zandra
probability
the average pass % in a test is 70. find out the probability tht out of a group of 8 students atleast 5 pass.
• Dec 9th 2008, 10:32 PM
mr fantastic
Quote:

Originally Posted by Zandra
the average pass % in a test is 70. find out the probability tht out of a group of 8 students atleast 5 pass.

Do you mean that the average number of students who pass a test is 70% ? If so, then:

Let X be the random variable number of students who pass.

X ~ Binomial(n = 8, p = 0.7)

Calculate $\Pr(X \geq 5)$.
• Dec 9th 2008, 10:37 PM
Quote:

Originally Posted by Zandra
the average pass % in a test is 70. find out the probability tht out of a group of 8 students atleast 5 pass.

Try Binomial distribution
X-B(8 , 7/10)
Let x be the random variable of students passing the test .

$P(X\geq5)$
• Dec 9th 2008, 11:21 PM
Zandra
thankyou