Question

Below is the relative-frequency table of the probability distribution for the discrete random variable X, with X = "the number of cars owned by families in New York."

x P(X = x)
0 0.03
1 0.31
2 0.43
3 0.14
4 0.09
If the expected value is 1.95, what is the standard deviation?

0.93
0.99
0.96

Answer 1

Answer: To calculate the standard deviation of a discrete random variable, we need to know the expected value and the variance. The variance of a discrete random variable X is given by:

Var(X) = Σ [ (x - E(X))^2 * P(X = x) ]

where the summation is taken over all possible values of X, and E(X) is the expected value of X.

We are given that the expected value of X is 1.95. Using the formula for the variance and the probabilities given in the table, we can calculate the variance as follows:

Var(X) = (0 - 1.95)^2 * 0.03 + (1 - 1.95)^2 * 0.31 + (2 - 1.95)^2 * 0.43 + (3 - 1.95)^2 * 0.14 + (4 - 1.95)^2 * 0.09

Var(X) = 1.1429

To find the standard deviation, we take the square root of the variance:

SD(X) = sqrt(Var(X))

SD(X) = sqrt(1.1429)

SD(X) ≈ 1.07

Therefore, the standard deviation of the number of cars owned by families in New York is approximately 1.07. None of the options given match this value exactly, but 0.99 is the closest.

Explanation: