Easy
Data: 4, 7, 2, 9, 3, 7, 5 — find the mean
Calculate the arithmetic mean (average) of this data set.
Formula
Mean = sum ÷ count = (4+7+2+9+3+7+5) ÷ 7 = 37 ÷ 7 ≈ 5.29.
Medium
Standard deviation of: 2, 4, 4, 4, 5, 5, 7, 9
Calculate the population standard deviation for this data set.
Steps
Mean = 5. Squared deviations: 9,1,1,1,0,0,4,16. Average = 4. SD = sqrt(4) = 2.
Medium
P(A) = 0.4, P(B) = 0.3. Find P(A or B) if mutually exclusive.
Calculate the probability that A or B occurs.
Rule
For mutually exclusive events: P(A or B) = P(A) + P(B) = 0.4 + 0.3 = 0.7.
Hard
Z-score: x = 80, mean = 75, SD = 5
Calculate the z-score and interpret what it means.
Formula
z = (x - mean) / SD = (80 - 75) / 5 = 1.0. This score is exactly 1 standard deviation above the mean.