WGU D582 INTRO TO STATS FOR
RESEARCH - HELPFUL TIPS
COMPREHENSIVE STUDY GUIDE 2026 FULL
QUESTIONS AND SOLUTIONS GRADED A+
◍ DISCRETE or CONTINUOUS? → Weight of a soil sample.
Answer: Continuous
◍ t-test: p-value = 0.006, α = 0.05. Conclusion?.
Answer: Reject H₀ — significant difference exists (0.006 < 0.05)
◍ CI example: 95% CI for difference is 0.2 to 0.9 (does NOT contain 0).
Conclusion?.
Answer: Reject H₀ — significant difference at α = 0.05
◍ Tukey's method: if a confidence interval for a difference does NOT contain
zero, what does that mean?.
Answer: That pair of means IS significantly different
◍ Z-score comparison: Score 89 (z=1.2) vs Score 82 (z=1.9) — which is better
relative performance?.
Answer: Score 82 (z=1.9) — higher z-score wins
◍ What does a 95% confidence interval mean?.
Answer: If the process were repeated many times, 95% of the resulting
intervals would contain the true population parameter
◍ What is SIMPLE RANDOM SAMPLING?.
Answer: Every individual has an equal chance of selection; e.g., drawing
names from a hat or using a random number generator
◍ What sample size info is needed to estimate a SINGLE mean?.
, Answer: Confidence level, standard deviation, and margin of error (NOT
population size)
◍ What is an ORDINAL variable?.
Answer: Categorical with a meaningful order/rank, but differences aren't
equal (e.g., perceived satisfaction level, education level ranking)
◍ For two normal curves: which has GREATER standard deviation?.
Answer: The one that is WIDER and SHORTER
◍ DISCRETE or CONTINUOUS? → Distance traveled.
Answer: Continuous
◍ What is a QUALITATIVE (categorical) variable?.
Answer: A variable that represents a category or group (e.g., college major,
food group, political affiliation, department, type of residence)
◍ When data has ONE variable with observed counts to compare to expected
equal distribution, which chi-square test is used?.
Answer: Goodness-of-fit test
◍ When ANOVA rejects H₀, what does the conclusion state?.
Answer: "At least one pair of means has a significant difference" (NOT all
pairs, NOT exactly one pair — unless Tukey's is done)
◍ What does it mean if a distribution is SYMMETRIC (normal)?.
Answer: The left and right sides mirror each other; mean ≈ median ≈ mode
◍ Interpret: y = 101 − 0.52x (x = time on test, y = score).
Answer: Each additional minute is associated with a 0.52 decrease in test
score
◍ What is the correct interpretation of a 95% CI for a difference in means?.
Answer: "We are 95% confident the true difference in means falls within
this interval." NOT "95% chance this specific interval is correct."
◍ Interpret: y = 88 − 0.05x (x = supplement dose, y = coordination score).
Answer: Each 1 mg increase in dose is associated with a 0.05 decrease in
test score
RESEARCH - HELPFUL TIPS
COMPREHENSIVE STUDY GUIDE 2026 FULL
QUESTIONS AND SOLUTIONS GRADED A+
◍ DISCRETE or CONTINUOUS? → Weight of a soil sample.
Answer: Continuous
◍ t-test: p-value = 0.006, α = 0.05. Conclusion?.
Answer: Reject H₀ — significant difference exists (0.006 < 0.05)
◍ CI example: 95% CI for difference is 0.2 to 0.9 (does NOT contain 0).
Conclusion?.
Answer: Reject H₀ — significant difference at α = 0.05
◍ Tukey's method: if a confidence interval for a difference does NOT contain
zero, what does that mean?.
Answer: That pair of means IS significantly different
◍ Z-score comparison: Score 89 (z=1.2) vs Score 82 (z=1.9) — which is better
relative performance?.
Answer: Score 82 (z=1.9) — higher z-score wins
◍ What does a 95% confidence interval mean?.
Answer: If the process were repeated many times, 95% of the resulting
intervals would contain the true population parameter
◍ What is SIMPLE RANDOM SAMPLING?.
Answer: Every individual has an equal chance of selection; e.g., drawing
names from a hat or using a random number generator
◍ What sample size info is needed to estimate a SINGLE mean?.
, Answer: Confidence level, standard deviation, and margin of error (NOT
population size)
◍ What is an ORDINAL variable?.
Answer: Categorical with a meaningful order/rank, but differences aren't
equal (e.g., perceived satisfaction level, education level ranking)
◍ For two normal curves: which has GREATER standard deviation?.
Answer: The one that is WIDER and SHORTER
◍ DISCRETE or CONTINUOUS? → Distance traveled.
Answer: Continuous
◍ What is a QUALITATIVE (categorical) variable?.
Answer: A variable that represents a category or group (e.g., college major,
food group, political affiliation, department, type of residence)
◍ When data has ONE variable with observed counts to compare to expected
equal distribution, which chi-square test is used?.
Answer: Goodness-of-fit test
◍ When ANOVA rejects H₀, what does the conclusion state?.
Answer: "At least one pair of means has a significant difference" (NOT all
pairs, NOT exactly one pair — unless Tukey's is done)
◍ What does it mean if a distribution is SYMMETRIC (normal)?.
Answer: The left and right sides mirror each other; mean ≈ median ≈ mode
◍ Interpret: y = 101 − 0.52x (x = time on test, y = score).
Answer: Each additional minute is associated with a 0.52 decrease in test
score
◍ What is the correct interpretation of a 95% CI for a difference in means?.
Answer: "We are 95% confident the true difference in means falls within
this interval." NOT "95% chance this specific interval is correct."
◍ Interpret: y = 88 − 0.05x (x = supplement dose, y = coordination score).
Answer: Each 1 mg increase in dose is associated with a 0.05 decrease in
test score
