Step-by-step explanation:
It came from nowhere. It makes no sense to add up the balance numbers. To illustrate, let's use a different example:
Adding up the money you spent, and you get $500. Add up the balances, and you get $1000. But why would you add the balances? The 300 in the second line is included in the 400 in the first line. You can't add them together. You'd be counting the 300 twice.
Answer:
Step-by-step explanation:
In statistics and probability analysis, the expected value "is calculated by multiplying each of the possible outcomes by the likelihood each outcome will occur and then summing all of those values".
The variance of a random variable Var(X) is the expected value of the squared deviation from the mean of X, E(X).
And the standard deviation of a random variable X is just the square root of the variance.
Let X be a random variable which denotes the money you may win or lose on each spin.
In the game of roulette, a wheel consists of 38 slots. To play the game, a metal ball is spun around the wheel and is allowed to fall into one of the numbered slots. If the number of the slot the ball falls into matches the number you selected, we win $35; otherwise we lose $1. So we have just one possibility to win and 37 of lose on an individual game.
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X P(X)
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35 1/38
-1 37/38
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In order to calculate the expected value we can use the following formula:
And if we use the values obtained we got:
In order to find the standard deviation we need to find first the second moment, given by :
And using the formula we got:
Then we can find the variance with the following formula:
And then the standard deviation would be given by: