Based on your anwser I realized that I must learn some more about ...
probabilities.
My idea was to know more about statistical functions in Excel and after that
calcuate what I need.
I think, know, that I will first take a look at a book about probabilities.
Thanks again for your anwser.
"Mike H" wrote:
Hi,
If you flip 9 times a coin and get 9 faces then at the 10Th time you flip it
the odds of getting a tail are much higher than the odds of getting a face.
Incorrect!!
The odds of 9 straight head flips is easy to calculate
=0.5^9
or around 0.19% chance
But having done that the odds of the tenth are 50/50 because the coin has no
memory and the result of the next event is not influenced by the previous
events. You're actually referring to the 'gamblers fallacy' which is believed
to suggest that ultimately the number of events will even out. Ten
consecutive black on the roulette wheel so lets bet large on red is a very
quick way indeed to end up bankrupt.
What will move near to 'normal' is the percentage for each event (50%) but
there could be a very large difference in the frequency of each that equate
to 50% especially when dealing with large numbers.
The odds of doing 10 straight head flips is
=0.5^10
Mike
"Raul Sousa" wrote:
If you flip 9 times a coin and get 9 faces then at the 10Th time you flip it
the odds of getting a tail are much higher than the odds of getting a face.
At any flip the chances are 50/50. But, the chances to get 10 faces straight
are lower than the chances to get 9 faces and 1 tail in 10 coin flips.
I am sure there must be a way to calculate this probabilities in excel. Just
dont know how to and appreciate any help.
"Mike H" wrote:
Hi,
The changes to have 1 or 0 are 50/50. In this case there is more 1 than 0
(5Vs2). So the chances that the next number is a zero are bigger than the
chances that the next number is 1.
That's incorrect because it implies that (say) a coin has memory and if we
flip 10 consecutive heads the next is more likely to be tails which it isn't,
the chance of the next being tails is exactly the same as for the previous 10
flips 50/50.
Mike
"Raul Sousa" wrote:
Thanks for your replay Max.
it could be a good idea. Unfortunately I think it is not correct.
The changes to have 1 or 0 are 50/50. In this case there is more 1 than 0
(5Vs2). So the chances that the next number is a zero are bigger than the
chances that the next number is 1.
I just dont know a formula to calculate these odds.
"Max" wrote:
Probability that its a 1:
=COUNTIF(A2:A8,1)/COUNTA(A2:A8)
Similarly, the probability that its a zero:
=COUNTIF(A2:A8,0)/COUNTA(A2:A8)
Alternatively, since Pzero + Pone = 1
as the data comprises only zeros or 1s (in this instance)
Pzero = 1 - COUNTIF(A2:A8,1)/COUNTA(A2:A8)
any good? hit the YES below
--
Max
Singapore
http://savefile.com/projects/236895
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xdemechanik
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"Raul Sousa" wrote:
I am trying to calculate probabilities in excel but I dont really know which
functions to use.
Lets say I have only two possible outcomes 1 and 0. So far the outcome was
as follow:
1
0
1
0
1
1
1
Which are the odds to get 1 and to get 0?
Which formula can calculate this?