BIG, let's knock this out.
The random variable X follows a binomial distribution, X∼B(n,p), where n=8 (number of trials) and p=1/4 (probability of success). The probability mass function is given by:
P(X=k)=(kn)pk(1−p)n−k
Here, n=8, p=1/4, and 1−p=1−1/4=3/4.
a) Find P(X=2)
Step 1: Identify the values for n, k, and p.
For P(X=2), we have n=8, k=2, p=1/4, and 1−p=3/4.
Step 2: Substitute the values into the binomial probability formula.
P(X=2)=(28)(41)2(43)8−2
P(X=2)=(28)(41)2(43)6
Step 3: Calculate the binomial coefficient (28).
(28)=2!(8−2)!8!=2!6!8!=2×18×7=28
Step 4: Calculate the powers and multiply.
P(X=2)=28×(161)×(4636)
P(X=2)=28×161×4096729
P(X=2)=16×409628×729=4×40967×729=163845103
P(X=2)≈0.31146
The probability is 163845103.
b) Find P(X≥1)
Step 1: Use the complement rule.
It is easier to calculate P(X≥1) as 1−P(X<1). Since X is a discrete random variable, P(X<1) is equivalent to P(X=0).
P(X≥1)=1−P(X=0)
Step 2: Calculate P(X=0).
For P(X=0), we have n=8, k=0, p=1/4, and 1−p=3/4.
P(X=0)=(08)(41)0(43)8−0
P(X=0)=1×1×(43)8
P(X=0)=4838=655366561
Step 3: Subtract P(X=0) from 1.
P(X≥1)=1−655366561
P(X≥1)=6553665536−6561=6553658975
P(X≥1)≈0.90003
The probability is 6553658975.
What's next? Send 'em!