STAT 200 PRACTICE EXAM 2026/2027
QUESTIONS AND ANSWERS
1. A researcher divides a population into groups based on geographic location and then
randomly selects several groups to interview every individual within those groups. Which
sampling method is this?
A. Stratified Sampling
B. Systematic Sampling
C. Convenience Sampling
D. Cluster Sampling
Answer: D
Conceptual Explanation: Cluster sampling involves dividing the population into groups
(clusters), randomly selecting clusters, and surveying all members within the selected
clusters.
2. Which of the following measures of central tendency is most resistant to extreme outliers?
A. Mean
B. Variance
,C. Range
D. Median
Answer: D
Conceptual Explanation: The median is the middle value and is not influenced by the
magnitude of extreme values, unlike the mean which sums all values.
3. If a distribution is negatively skewed (skewed to the left), which relationship is generally
true?
A. Mean > Median
B. Mean = Median
C. Mode < Mean
D. Mean < Median
Answer: D
Conceptual Explanation: In a left-skewed distribution, the long tail is on the left, pulling
the mean down below the median.
4. In a standard normal distribution (Z), what is the area to the left of Z = -1.96?
A. 0.0500
B. 0.0250
C. 0.9750
, D. 0.0100
Answer: B
Conceptual Explanation: For a standard normal distribution, the area outside ±1.96 is 5%.
Therefore, the area in the left tail (less than -1.96) is 2.5% or 0.0250.
5. A Type II error occurs when:
A. We reject a true null hypothesis.
B. We fail to reject a true null hypothesis.
C. We reject a false null hypothesis.
D. We fail to reject a false null hypothesis.
Answer: D
Conceptual Explanation: Type II error (Beta) happens when the null hypothesis is
actually false, but the test fails to detect the effect and fails to reject H0.
6. What is the primary purpose of the Central Limit Theorem?
A. To prove that all populations are normally distributed.
B. To show the sampling distribution of the mean approaches normality as sample size
increases.
C. To ensure the sample mean is always equal to the population mean.
D. To reduce the standard deviation of the population.
QUESTIONS AND ANSWERS
1. A researcher divides a population into groups based on geographic location and then
randomly selects several groups to interview every individual within those groups. Which
sampling method is this?
A. Stratified Sampling
B. Systematic Sampling
C. Convenience Sampling
D. Cluster Sampling
Answer: D
Conceptual Explanation: Cluster sampling involves dividing the population into groups
(clusters), randomly selecting clusters, and surveying all members within the selected
clusters.
2. Which of the following measures of central tendency is most resistant to extreme outliers?
A. Mean
B. Variance
,C. Range
D. Median
Answer: D
Conceptual Explanation: The median is the middle value and is not influenced by the
magnitude of extreme values, unlike the mean which sums all values.
3. If a distribution is negatively skewed (skewed to the left), which relationship is generally
true?
A. Mean > Median
B. Mean = Median
C. Mode < Mean
D. Mean < Median
Answer: D
Conceptual Explanation: In a left-skewed distribution, the long tail is on the left, pulling
the mean down below the median.
4. In a standard normal distribution (Z), what is the area to the left of Z = -1.96?
A. 0.0500
B. 0.0250
C. 0.9750
, D. 0.0100
Answer: B
Conceptual Explanation: For a standard normal distribution, the area outside ±1.96 is 5%.
Therefore, the area in the left tail (less than -1.96) is 2.5% or 0.0250.
5. A Type II error occurs when:
A. We reject a true null hypothesis.
B. We fail to reject a true null hypothesis.
C. We reject a false null hypothesis.
D. We fail to reject a false null hypothesis.
Answer: D
Conceptual Explanation: Type II error (Beta) happens when the null hypothesis is
actually false, but the test fails to detect the effect and fails to reject H0.
6. What is the primary purpose of the Central Limit Theorem?
A. To prove that all populations are normally distributed.
B. To show the sampling distribution of the mean approaches normality as sample size
increases.
C. To ensure the sample mean is always equal to the population mean.
D. To reduce the standard deviation of the population.
