Chapter 7
7.1 a 0, 1, 2, …
b Yes, we can identify the first value (0), the second (1), and so on.
c It is finite, because the number of cars is finite.
d The variable is discrete because it is countable.
7.2 a any value between 0 and several hundred miles
b No, because we cannot identify the second value or any other value larger than 0.
c No, uncountable means infinite.
d The variable is continuous.
7.3 a The values in cents are 0 ,1 ,2, …
b Yes, because we can identify the first ,second, etc.
c Yes, it is finite because students cannot earn an infinite amount of money.
d Technically, the variable is discrete.
7.4 a 0, 1, 2, …, 100
b Yes.
c Yes, there are 101 values.
d The variable is discrete because it is countable.
7.5 a No the sum of probabilities is not equal to 1.
b Yes, because the probabilities lie between 0 and 1 and sum to 1.
c No, because the probabilities do not sum to 1.
7.6 P(x) = 1/6 for x = 1, 2, 3, 4, 5, and 6
7.7 a
x
P(x)
0
24,750/165,000 = .15
1
37,950/165,000 = .23
2
59,400/165,000 = .36
3
29,700/165,000 = .18
4
9,900/165,000 = .06
5
3,300/165,000 = .02
b
(i) P(X
≤
2) = P(0) + P(1) + P(2) = .15 + .23 + .36 = .74
(ii) P(X > 2) = P(3) + P(4) + P(5) = .18 + .06 + .02 = .26
(iii) P(X
≥
4) = P(4) + P(5) = .06 + .02 = .08
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