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Posted by **Shannon** on Sunday, December 5, 2010 at 10:02am.

Grade Frequency

A 2

B 8

C 11

D 2

F 1

I think it is 1 out of 5 or 4 but I am not sure? Please help :) Thank you much!

- Math -
**MathMate**, Sunday, December 5, 2010 at 10:04amThere are 5 possible outcomes, one of which is a B.

So what is P(B), and what is P(not B)?

Hint : P(B) and P(not B) have to add up to 1.

- Math -
**Shannon**, Sunday, December 5, 2010 at 10:10amOh ok I think I get it, so P(B)=0.5, 1/2,

and P(not B)=0.5,1/2???

Is that right?

- Math -
**MathMate**, Sunday, December 5, 2010 at 11:13amSorry, not really.

Figure out the probability of P(B) which is to get B out of 5 possible choices.

The rest would be easy to figure out.

- Math -
**Jen**, Sunday, December 5, 2010 at 1:20pmAdd up all the grades that aren't B's. Then put that over the total amount of grades.

- Math -
**Shannon**, Sunday, December 5, 2010 at 3:51pmOk so it would be P(B)=0.8, the probability that the grade is not a B.?

I hope this is right now, if it isn't I give up....lol !

- Math -
**MathMate**, Sunday, December 5, 2010 at 5:13pmDon't give up, you're right.... almost!

What Jen showed you to do was

P(not B), which equals 0.8

("...grades that aren't B's...")

there is only one grade B, so it is 1/5, there are 4 grades that are not B, so

P(not B)=4/5=0.8

Sorry if it was too confusing, hope it's more clear now.

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