# probability query?

• Nov 12th 2008, 08:49 PM
steph_r
probability query?
Hey everyone..

just wondering if i could get some assistance with this question..

The probability of getting a head on a flip of "biased" coin is 0.3.
If the coin is tossed 50 times, what is the expected probability of getting a head, after 40 throws

would you do:

Probability = (0.3 x 40) / 50 ?

It was a question on a test that i did and want to check i did the right or wrong thing.

Cheers
• Nov 12th 2008, 09:50 PM
mr fantastic
Quote:

Originally Posted by steph_r
Hey everyone..

just wondering if i could get some assistance with this question..

The probability of getting a head on a flip of "biased" coin is 0.3.
If the coin is tossed 50 times, what is the expected probability of getting a head, after 40 throws

would you do:

Probability = (0.3 x 40) / 50 ?

It was a question on a test that i did and want to check i did the right or wrong thing.

Cheers

I'm sorry but I can't make sense of ".. expected probability of getting a head .." Do you mean expected number of heads after 40 throws ....?
• Nov 12th 2008, 09:55 PM
steph_r
probability
Quote:

Originally Posted by mr fantastic
I'm sorry but I can't make sense of ".. expected probability of getting a head .." Do you mean expected number of heads after 40 throws ....?

yes i think so :S Or perhaps, what is the estimated probability?
it was a question on a test (assessment task) and i couldnt really remember the question.. sorry for the inconvenience
• Nov 12th 2008, 10:04 PM
mr fantastic
Quote:

Originally Posted by steph_r
yes i think so :S Or perhaps, what is the estimated probability?
it was a question on a test (assessment task) and i couldnt really remember the question.. sorry for the inconvenience

The expected number of heads after 40 throws is (40)(0.3).

Estimating a probability makes no sense since:

1. You're told the probability of a head each throw is 0.3

Wait until you get the test back so you can post the question correctly. By the way, what's stopping you from asking your teacher in the meantime?
• Nov 12th 2008, 10:17 PM
steph_r
Quote:

Originally Posted by mr fantastic
The expected number of heads after 40 throws is (40)(0.3).

Estimating a probability makes no sense since:

1. You're told the probability of a head each throw is 0.3