### Scribe Post for October 10, 2008

Monday, October 13, 2008
Probability
In class today we learned about Theoretical and Experimental Probability. Theoretical probability is what should happen, hence the word "Theory." Experimental probability is what happened after the experiment, sort of like the result. We learned that the more times we do an experiment, the closer the experimental probability is to the theoretical probability. To help us understand better, Mr.Harbeck used a gumball machine as an example.

(Drawn by chinn2)

The gumball machine has 10 balls in total. Four of them are blue, 3 are yellow, 2 are green and one red. Every time we pull a gumball out, it replenishes what was taken out. To find the the theoretical probability you need to make a fraction, favorable outcome(F.O.) over total possible outcome(T.P.O.).

Ex.
I want red, so red is my favorable outcome. Red has one out of 10 chance of being picked. 1/10 one being the F.O. and 10 being the T.P.O. One out of ten in fraction is 10%. This is the theoretical probability of a red gumball coming out. This goes the same for all the other colors.

So when we take out 10 gumballs only one of them should be red, right? Wrong!! That was only the theoretical probability. This is when experimental probability kicks in. To find this you need to conduct some experiments or trials. After this make a fraction of F.O. over # of trials.

Ex.
I want red, so again red is the favorable outcome. I took out 10 gumballs and I got 2Reds, 5Blues, 2Yellows and one Green. Out of ten gumballs, I got 2red ones. In other words, 2 F.O. out of 10 Trials. 2/10 = 20% = Experimental Probability.

This is the first part of the class on Friday. The second part is the most beloved one, HOMEWORK!!

Which Italian Insects Often Fall in Love?

The first question I'm going to show is #8.
"Jack rolled a regular 6-faced die three times and got 2 each time.
What is the probability he will get 2 on the next roll?

Answer: The probability he will roll a 2 again is 1/6 or 16.7%
. Although he got twos in the last three times it doesn't change his theoretical probability.

The next question is #11.
"Jill tossed a coin 10 times and got heads every time. What is the probability she will get heads on the next toss?"

The probability he will get heads again is 1/2 or 50%. Even if he was in a streak, his theoretical probability is still the same.

The last question is #12.
"A traffic signal is green for 20 seconds, then amber for 5 seconds, then red for 30 seconds. When you reach the signal, what is the probability it is:

• a)-Green,
• b) - Amber,
Answer: A) The probability it will be green is 20/55 seconds or 4/11. That is 36.36% repeated.
B) The probability it will be amber is 5/55 seconds or 1/11. That is 09.09% repeated.

This is mostly what we covered in class. I may have missed a few minor details but i hope this helps. Now I have the power to pick whoever I want to be the next scribe and I choose my BEST FRIEND, FRANCIS!!!

1. gian 8-16 said...

good job nikko (:

October 14, 2008 at 10:18 PM

2. Lissa 8-16 said...

GOOD JOB NICKO ! (: awesomest post ever ! lol :D

October 15, 2008 at 7:40 PM

3. Lissa 8-16 said...

OH BY THE WAY , very colourful (:

October 15, 2008 at 7:41 PM