1. ## Binomial Probability questions

1. A dental inspector finds that about 20% of children of a certain area have tooth decay. What is the probability that out of 6children examined, only the first,third and fifth will have tooth decay?

-> i got (0.2)^2(0.8)^3 =64/3125 but the answer is 64/3125. What am i missing??

2. On the average a typist has to correct one word in 800words. Assuming that a page contains 200words, find the probability of more than one correction per page.

-> i got
1- [200C1(799/800)^199(1/800) + 200C0(799/800)^200] = 0.0264

2. ## Re: Binomial Probability questions

1.It's Exactly What You need
Did You multiplied 200 in first statment?

3. ## Re: Binomial Probability questions

Originally Posted by gahyunkk
2. On the average a typist has to correct one word in 800words. Assuming that a page contains 200words, find the probability of more than one correction per page.

-> i got
1- [200C1(799/800)^199(1/800) + 200C0(799/800)^200] = 0.0264
I think you've done (2) correctly.

4. ## Re: Binomial Probability questions

[QUOTE=gahyunkk;828536]1. A dental inspector finds that about 20% of children of a certain area have tooth decay. What is the probability that out of 6children examined, only the first,third and fifth will have tooth decay?

-> i got (0.2)^2(0.8)^3 =64/3125 but the answer is 64/3125. What am i missing??
There are three children with tooth decay so this should be $\displaystyle (0.2)^3(0.8)^3= (1/5)^3(4/5)^3= 2^9/5^6$. Your "64/3125 but the answer is 64/3125" is very confusing.

2. On the average a typist has to correct one word in 800words. Assuming that a page contains 200words, find the probability of more than one correction per page.

-> i got
1- [200C1(799/800)^199(1/800) + 200C0(799/800)^200] = 0.0264

5. ## Binomial Probability questions

Originally Posted by Cartesius24
1.It's Exactly What You need
Did You multiplied 200 in first statment?
Oh sorry first one if i do 0.2^3x0.8^3 i get

And what do u mean by multiplying 200??

6. ## Binomial Probability questions

[QUOTE=HallsofIvy;828587]

Sorry i typed wrong thing
I originally did 0.2^3x0.8^3 but then i get 64/15625 but the answer is 64/3125

2^6=15625

8. ## Re: Binomial Probability questions

[QUOTE =Cartesius24;828694]2^6=15625[/QUOTE]
Why is it 2^6???

sorry 5^6