Question

This morning, Mr. Trevino released the scores from last week's spelling test. Score Number of students 19 2 43 1 56 1 70 3 92 1 100 2 X is the score that a randomly chosen student scored. What is the expected value of x? Write your answer as a decimal.

Answer 1

The basic expected value formula is the probability of an event multiplied by the number of times the event happens: (P(x) * n)

Sum of the number of students = 2 + 1 + 1 +3 + 1 + 2 = 10

Probability of scoring 19 = 2/ 10 = 0.2

probability of scoring 43 = 1/10 = 0.1

probability of scoring 56 = 1/10 = 0.1

probability of scoring 70 = 3/10 = 0.3

probability of scoring 92 = 1/10 = 0.1

probability of scoring 100 = 2/10 = 0.2

Appling the expected value formula

Expected value of X = 19 x 0.2 + 43 x 0.1 + 56 x 0.1 + 70 x 0.3 + 92x 0.1 + 100 x 0.2

=> 63.9

Expected value of X = 63.9