# Poisson or Binomial

#### Hans Rudel

##### New Member
Hi, im trying to make sure i have the difference between when to use Binomial and Poisson distributions firmly understood. Regarding the following question, im assuming its a Binomial since its possible to determine p and q even though a rate is specified?

Question) If a baseball batter hit 4 balls per 10 pitched, whats the probability of him hitting 6 balls per 20 pitches?

If i changed the question to the following, am i correct in assuming it would be Poisson?

Question2) If a baseball batter hit 4 balls per day, whats the probability of him hitting 6 in 2 days?

Thanks for your help!

#### geosun

##### New Member
mean or average probability of something happening is poisson while
exact probability of something happening is binomial

#### Outlier

##### TS Contributor
im assuming its a Binomial since its possible to determine p and q even though a rate is specified?

Question) If a baseball batter hit 4 balls per 10 pitched, whats the probability of him hitting 6 balls per 20 pitches?

Question2) If a baseball batter hit 4 balls per day, whats the probability of him hitting 6 in 2 days?
Based on

"the Poisson binomial distribution is the discrete probability distribution of a sum of independent Bernoulli trials.
In other words, it is the probability distribution of the number of successes in a sequence of n independent yes/no experiments with success probabilities .

The ordinary binomial distribution is a special case of the Poisson binomial distribution, when all success probabilities are the same. . ."

they both sound like Poisson to me because success probabilities vary with each pitch.

#### Hans Rudel

##### New Member
@Geosun, so do you think both are poisson or not?

@Outlier, where did you get the quote from??

Thanks guys

#### geosun

##### New Member
both are poisson because they arn't exact probabilities, their the average batting on a random day or time period.

#### Outlier

##### TS Contributor
@Outlier, where did you get the quote from??

Thanks guys
Wikipedia.
If you search on a few words in sequence and put them in quotes you can usually pull up the source. I try to pick an unusual sequence.