STAT
Rec_probability_au10

# Now choose two children at random and count how many

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Now choose TWO children at random and count how many of them own a cat. (We are not concerned with dogs for this.) a) What’s the chance both children own a cat? ANS___________ b) What’s the chance that exactly one child owns a cat? ANS___________ c) What’s the chance that at least one child owns a cat? ANS___________ 3. ( Show all your work to get credit, work means symbols !) The children in a school are to have extra swimming lessons if they cannot swim. We took a sample of 100 students from the 7-8 year old age group. We found out 40% of the entire group couldn’t swim. Of those who couldn’t swim, 75% were 7 year olds. Of those who could swim, 50% were 8 year olds.

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Use the following symbols to answer the following questions. Y= can swim N= can’t swim 7 = seven year old 8 = eight year old a) Write down the probabilities known from the problem. P(N)= ________________ P(7| N)= ______________ P(8|Y)=_______________ b) Make a table of this situation and fill in all its probabilities, including those in the margins. c) What’s the chance that a randomly selected student is 8 years old and can’t swim? ANS___________ d) What percentage of the 7 year olds can swim? ANS___________ e) Is being able to swim independent of age for this group? Show using probabilities and 10 words or less. 4. Suppose 15% of all females read People magazine and 5% of all males read People magazine. This tells you that reading People is independent of gender. a. TRUE b. FALSE
5. 40% of American teenagers have accounts on Facebook (FB) and 10% of American teenagers have accounts on Twitter (TW). We also know that 80% of the teenagers who have Twitter accounts also have Facebook accounts.

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