Answers:
(a) 0.5
(b) 0.3
(c) 0.6
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Step-by-step explanation:
Part (a)
There are 21 parents who bought a t-shirt and 14 parents who bought a sweatshirt. That's 21+14 = 35 parents total out of 70 people total.
Therefore, 35/70 = 0.5 is the probability of randomly selecting a parent from this sample.
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Part (b)
There are 21 parents who bought a t-shirt out of 70 people total
21/70 = 0.3
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Part (c)
The vertical line represents "given".
This means P(t-shirt | parent) is the same as P(t-shirt given parent).
It tells us that whoever we selected, this person is a parent and we focus solely on the "parent" column.
There are 21 parents who bought a t-shirt out of 21+14 = 35 parents total
21/35 = 0.6
This basically says "60% of the parents bought a t-shirt".