what are the odds of having a heart attack when 30 people had one out of 1000 people

Odds and probability are somewhat different.....

The probability that someone has a heart attack  is 30 / 100

The odds that someone has a heart attack are   30 : [1000 - 30]  =  30 : 970  = 30 to 970

 3/100

3people out of 100

30 out of 1000   ARE the odds

equal to   3  out of 100

    or 3 %

Questioning CPhill (though he is usually correct!)

I see how the PROBABILITY is 30 out of 1000 will get an MI.

That leaves 970   who MIGHT get an MI.   If the probability was 3% why wouldn't the odds be 3% of 970??    i.e.  29.1 to 970         Instead of 30 to 970??

Thanx    ~jc

Note, jc

Consider a single die......let's look at the probability of rolling a "1"   .....this is given by

[Number of ways a specific outcome could occur ] / [ Number of total outcomes]  =  1 / 6

But odds are different......the odds in favor  of an event happening  are given as:

[Number of ways a specific outcome could occur] : [ Number of all other possible outcomes]

So......rolling a "1" could happen in 1 way.......and the number of other outcomes possible is 5...we could roll a 2, 3, 4, 5, or 6,   instead

So......the odds in favor of rolling a 1   =   1 : 5   =  1 to 5

So...in our problem......the odds in favor of having a heart attack  =

[30 people have a heart attack ] : [ 970 people don't]  = 30 :  970

Does that make sense ???

[ People often  use the terms "probability' and "odds" interchangeably. They are not the same, technically.....!!!  ]