Question

2. Natalie is taking 4 courses for the semester. She believes that the probability mass function for Xthe number of courses for which she will get an A grade is given below. 0.10 0.15 0.05 0.40 a) What is the probability that Ellen gets at least 2 A's? (Write the probability sentence related) (3pts) b) Complete the cumulative distribution function (cdf): (5pts) 3 4 c) What is the expected value, .e. EX) for the number of courses for which she will get an A grade? Interpret it in the context of the problem. Formula: Σ, k·P(X = k) d) If the variance is Var(X) 0.9875, what is the standard deviation?

Ellen is taking 4 courses for the semester. She believes that the probability mass function for X = the number of courses for which she will get an A grade is given below.

k 0 1 2 3 4 ?(? = ?) 0.10 ? 0.40 0.15 0.05

a) What is the probability that Ellen gets at least 2 A’s? (Write the probability sentence related) (3pts)

b) Complete the cumulative distribution function (cdf): (5pts) k 0 1 2 3 4 ?(? ≤ ?)

c) What is the expected value, i.e. E(X) for the number of courses for which she will get an A grade? Interpret it in the context of the problem. Formula: ∑ ? ∙ ?(? = ?) ? ?=1

d) If the variance is ???(?) = 0.9875, what is the standard deviation?

Answer 1

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