Quiz #14a
Answers
August 1, 2014
Math 141
1. A class contains the following students as listed in the table. Let the random variable X
denote the number of freshmen students selected in a sample of 6.
class
7 freshmen
5 sophomores
12 Juniors
Compute P (X = 2) =
Answer:
C(7, 2) ∗ C(17, 4)
C(24, 6)
2. Classify the random variable as discreet or continuous.
X = The number of cadets that can fit in a single elevator.
discrete
3. Here is the probability distribution for a random variable X.
X
prob
−4
10
0.2
17
0.1
25
0.15
36
0.30
(a) P (X = −4) = 0.25
(b) P (X > 17) = 0.15 + 0.30 = 0.45
4. draw the historgram for the probability distribution of therandom variable X.
X
prob
1
0.4
2
0.2
5
0.1
6
0.30
0.6
0.5
0.4
0.3
0.2
0.1
−1
1
2
3
4
5
6
7
8