Question

The final exam grade of a statistics class has a skewed distribution with mean of 79 and standard deviation of 8.2. If a random sample of 35 students selected from this class, then what is the probability that average final exam grade of this sample is between 76 and 82?

Answer 1

Solution :

Given that,

mean = = 79

standard deviation = = 8.2

= / n = 8.2 / 35 = 1.3861

= P[(76 - 79) / 1.3861< ( - ) / < (82 - 79) / 1.3861)]

= P(-2.16 < Z < 2.16)

= P(Z < 2.16) - P(Z < -2.16)

= 0.9846 - 0.0154

= 0.9692

Probability = 0.9692