2 fair dice are thrown. How do you calculate the probability that the event that the sum on the 2 dice is not equal to 8?
1 Answer
Explanation:
One of the ways to see what is going on is to draw a cross tabulation table.
Probability is usually expressed as a fraction (or decimal) of a whole count. All probabilities (fractions) when added up form the whole of what you are counting. This whole is represented by the value 1. In that you have 1 of the whole.
In this case the whole is all the content of the squares in the table.
The count of squares is
The count of 8's is 5
We are 'looking' at all the eights. So the sample is all the 8's and the population from which this sample is taken is all of the 36 squares.
The easiest way of count 'not 8' is to use the approach:
Probability of everything (1) - probability of 8 = probability not 8
Probability is 8
So
