True or False?
If I roll a fair standard dice any (positive) number of times and get their sum, the probability of obtaining an odd or even number is equal.
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Considering the implied question in the problem title.
FindFit [ Table [ First [ Timing [ lo g 2 ( Plus @@ Table [ ( Plus @@ t m o d 2 ) , { t , Tuples [ { 0 , 1 } , n ] } ] ) ] ] , { n , 2 5 } ] , e a x + b + c , { a , b , c } , x ]
a − > 0 . 7 1 6 9 6 7 9 6 2 8 8 1 , b − > − 1 4 . 4 0 4 8 4 0 1 8 7 7 , c − > − 0 . 0 0 8 9 0 4 0 3 7 8 4 3 6
e a x + b + c /. { a → 0 . 7 1 6 9 6 8 , b → − 1 4 . 4 0 4 8 , c → − 0 . 0 0 8 9 0 4 0 4 , x → 1 0 0 0 }
1 . 3 1 6 1 × 1 0 3 0 5
The last is the estimated time on my computer using Wolfram Mathematica in seconds for 1000 dice, which is vastly greater than the age of the universe.
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When rolling a die once, the probability of getting an even number (1, 3, 5) is the same as the probability of getting an odd number (2, 4, 6).
Assume that when rolling n dice, the probability of getting an even sum and the probability of getting an odd sum are both 2 1 . Now, roll n + 1 dice.
An odd result occurs when the sum of the first n dice and the final die have opposite parity. This happens with probability 2 1 × 2 1 + 2 1 × 2 1 = 2 1 (you can think of this as the probability the first n are odd times the probability the last one is even, plus the probability the first n are even times the probability the last one is odd).
Similarly, an even result occurs when the sum of the first n dice and the final die have the same parity. This also happens with probability 2 1 × 2 1 + 2 1 × 2 1 = 2 1 .
The statement is True .