## January 05, 2007

### Scribe post

Probability

1st period class

it was the day before the Holiday break so we didn't do much but as usually we started the day by doing question......^_^

Blood types in North America are distributed as follows:

Type O: 44% Type A: 42% Type B: 10% Type AB: 4%

a) are the blood types mutually exclusive?

b)what is the probability that a couple both have type O blood?

a) no (because the blood type can be both be "A" "B" or "AB" and "O" is the universal blood Donner meaning that it can fit into any blood type category)

b) "tree diagram"!! HO = "has blood type "O" NO = No blood type "O"

the first tree branch representing one of the couple has 0.44 chance of getting blood type "O" and the second branch representing the second couple has 0.44 chance getting type "O" also. we use "Multiplying Probability" since we want to find out what is the probability that both couples have the same type "O". (HO)HO) = Santa clause? HO NO HO NO I'm just kidding the answer is (0.44)(0.44) = .1936 or 19% that both of them have the same blood type "O".

2nd period class

In a group of 30 students what is is the probability that at least two have the same birthday?

*find the probability that nobody else have the same birthday

* use Pick formula since the order matters

*(# of days in a year)P(# of students) divided by (# of days in a year)^(# of students)

365P30/365^30 = 0.26 then subtract it from 1 ( 1- 0.26 =74%)

therefore the probability of at least two students have the same birthday is 74% (3o students)

and then one of my classmate asked him if our answer for this question was really true....in a 30 people group is there really a 74% chance of picking at least two people that have the same birthday? but most of our classmates are "missing"*wink**wink* so he started getting students on the hall way to make a group of 30 students and then he asked us one by one our birthdays but in our 30 group of students no one has the same birthday so he went back on the hallway to get some more people to raise the chances............were like HO HO HO HO laughing but we forgot to make a list and everyone was like HO NO HO NO no one made a list oi that was fun..............

sorry I couldn't get all the notes for this question :)

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THE SCRIBE IS TENNYSON .....................FOR MONDAY