help with statistic problem

• Nov 17th 2010, 10:16 AM
uga75
help with statistic problem
Hi, I'm confused with this problem, wanted to know if im on the right track. Any help will be appreciated . thank you

what is P(high calorie and high fiber)? For this I got (53 and 22)/ 84 = 0.89 = 89%
what is P(high calorie or high fiber)? and for this one i got ,18/53 = 0.33= 34% , 18/22=0.81=81%= 34%+81% = 115 - 89=26%
What is P(high calorie, given high fiber)? =18/53= 0.3396= 34%

decide if the events high calorie and high fiber are independent or dependent.
Calorie Level
Fiber Type High Calorie Low Calorie Totals
High Fiber 18 4 22
Medium Fiber 23 6 29
Low Fiber 12 21 33
Totals 53 31 84
• Nov 17th 2010, 10:30 AM
Unknown008
I assume that the total number of 'participants' is 84.

1. No. In all this set, how many people have both high calorie and high fibre?

The probability is then this number divided by the total of 84

2. No. This set will include all the ones having either high calorie or high fibre.

This means you have have:
High calorie high fibre
High calorie medium fibre
High calorie low fibre
Low calorie high fibre

All these divided by 84

3. No, you did the opposite. The question is the same as "Of all those having high fibre, how many also have high calorie?" Then, convert this into probability.

Can you try again?
• Nov 17th 2010, 11:04 AM
uga75
so the first one would be 18/84= 21%??
and the second one 57/84= 68%?? IS THAT right? thankks for the reply
• Nov 17th 2010, 11:06 AM
Unknown008
1. Right!

2. Right!

3. Now this last part, I'm sure you can do it (Smile)
• Nov 17th 2010, 04:42 PM
uga75
hi, in regards to those two answers .. I compared my answers to a classmate and we both have different solution. Im confused because i got two different answers and my classmate claims these are the correct answers. Any help appreciated. thank you
P(high calorie and high fiber) = P(high calorie) * P(high fiber) = 53/84 *22/84 = 1166/7056 = 0.165

P(high calorie or high fiber) = P(high calorie) + P(high fiber) - P(high calorie and high fiber) => 53/84 + 22/84 - 1166/7056 = 0.631 +0.262 -0.165 = 0.728
• Nov 17th 2010, 08:26 PM
Unknown008
No, by what you just did, you are including those who also have medium fibre, low fibre, and low calorie which is not good. Your previous answer was good.

Let's try this:

http://p1cture.me/images/58637125393186099806.png

This is a Venn Diagram representation of the data given to you.

1. Shade the area which represents $\displaystyle A = \text{High calorie} \cap \text{High fibre}$
The probability is that area over the total number.

2. Shade the area which represents $\displaystyle B = \text{High calorie} \cup \text{High fibre}$
The probability is that area over the total number.

3. Shade the area within the set of high fibre which represents $\displaystyle C = \text{High calorie}$
The probability is that area over the the total number in the set High fibre.