probability consumer will be female, will buy item between

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confused
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probability consumer will be female, will buy item between

Postby confused » Mon May 04, 2009 4:17 pm

1.: At a certain flea maket, 35% of purchases are $10 to $20. The probablity that a consumer will be a male is 60%. What is the probablity that a consumer will be a female and will make a purchase between $10 and $20?

2.: Two sacks each contain 4 candies, 2 packs of gum, and 7 cookies. One item is randomly selected from each sack. What is the probablity that both selected items will be cookies?

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stapel_eliz
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Postby stapel_eliz » Tue May 05, 2009 12:34 pm

1.: At a certain flea maket, 35% of purchases are $10 to $20. The probablity that a consumer will be a male is 60%. What is the probablity that a consumer will be a female and will make a purchase between $10 and $20?
I think this is one of those "grid" exercises. So set up as:
grid:
       $10 < x < $30?
        yes     no
       +-----+-----+
  male |     |     | 0.6
       +-----+-----+
female |     |     | 0.4
       +-----+-----+
        0.35   0.65
The events would appear to be independent, so multiply to fill things in:
grid:
       $10 < x < $30?
         yes      no
       +------+------+
  male | 0.21 | 0.39 | 0.6
       +------+------+
female | 0.14 | 0.26 | 0.4
       +------+------+
         0.35   0.65
Then read the answer-value from the grid. :wink:
2.: Two sacks each contain 4 candies, 2 packs of gum, and 7 cookies. One item is randomly selected from each sack. What is the probablity that both selected items will be cookies?
What is the probability of drawing a cookie from one sack?

Since the sacks are independent, then what is the probability of drawing cookies from both sacks?

:D


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