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Here are the results of a survey that students conducted at a mall. The students

ID: 3054079 • Letter: H

Question

Here are the results of a survey that students conducted at a mall. The students conducted this survey as part of a statistics project to determine if younger adults are more likely to have tattoos.

At least one tattoo

No tattoo

Row Totals

Age 18 - 29

170

320

490

Age 30 - 50

60

445

505

Column Totals

230

765

995

If we randomly select a person in the sample who is 30 to 50 years old, what is the probability that this person has a tattoo?

At least one tattoo

No tattoo

Row Totals

Age 18 - 29

170

320

490

Age 30 - 50

60

445

505

Column Totals

230

765

995

Explanation / Answer

We have to calculate P( Has tattoo | Age 30-50) = ?

From the conditional probability formula,

P(A | B) = P( A AND B) / P(B)

P( Has tattoo | Age 30-50) = P( Has tattoo AND Age 30-50) / P( Age 30-50)

= 60 / 505

= 0.1188

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