MATH 225N: STATISTICAL REASONING
FOR DECISION MAKING MIDTERM
EXAM QUESTIONS AND VERIFIED
ANSWERS |100% CORRECT| GRADE A+
1. A researcher wants to study the effects of a new medication on blood pressure. They divide
the participants into age groups (20-30, 31-40, 41-50, etc.) and then randomly select 10
individuals from each group. Which sampling method is being used?
A. Simple Random Sampling
B. Stratified Sampling
C. Systematic Sampling
D. Cluster Sampling
Answer: B
Conceptual Explanation: Stratified sampling involves dividing the population into groups
(strata) and taking a random sample from each stratum.
2. Data representing the different types of surgical procedures performed in a hospital last
year is classified at which level of measurement?
A. Ratio
B. Ordinal
,C. Interval
D. Nominal
Answer: D
Conceptual Explanation: Nominal data consists of categories or names without any
inherent order or numerical value.
3. If a dataset has a mean of 50 and a standard deviation of 5, what is the z-score for a value
of 42?
A. 1.6
B. -1.6
C. 8
D. -8
Answer: B
Conceptual Explanation: z = (x - mean) / sd = (42 - 50) / 5 = - = -1.6.
4. Which of the following is a characteristic of a discrete variable?
A. It has a countable number of possible values.
B. It is typically measured rather than counted.
C. It can take on any value within a given range.
D. It includes decimals and fractions in its measurement.
, Answer: A
Conceptual Explanation: Discrete variables are variables for which the values are
countable.
5. In a negatively skewed distribution, which of the following relationships is generally true?
A. Mean > Median > Mode
B. Mean = Median = Mode
C. Mode > Median > Mean
D. Median > Mode > Mean
Answer: C
Conceptual Explanation: In a negatively skewed (left-skewed) distribution, the mean is
pulled toward the tail, making it smaller than the median and mode.
6. According to the Empirical Rule, approximately what percentage of data falls within two
standard deviations of the mean in a bell-shaped distribution?
A. 95%
B. 68%
C. 99.7%
D. 50%
Answer: A
FOR DECISION MAKING MIDTERM
EXAM QUESTIONS AND VERIFIED
ANSWERS |100% CORRECT| GRADE A+
1. A researcher wants to study the effects of a new medication on blood pressure. They divide
the participants into age groups (20-30, 31-40, 41-50, etc.) and then randomly select 10
individuals from each group. Which sampling method is being used?
A. Simple Random Sampling
B. Stratified Sampling
C. Systematic Sampling
D. Cluster Sampling
Answer: B
Conceptual Explanation: Stratified sampling involves dividing the population into groups
(strata) and taking a random sample from each stratum.
2. Data representing the different types of surgical procedures performed in a hospital last
year is classified at which level of measurement?
A. Ratio
B. Ordinal
,C. Interval
D. Nominal
Answer: D
Conceptual Explanation: Nominal data consists of categories or names without any
inherent order or numerical value.
3. If a dataset has a mean of 50 and a standard deviation of 5, what is the z-score for a value
of 42?
A. 1.6
B. -1.6
C. 8
D. -8
Answer: B
Conceptual Explanation: z = (x - mean) / sd = (42 - 50) / 5 = - = -1.6.
4. Which of the following is a characteristic of a discrete variable?
A. It has a countable number of possible values.
B. It is typically measured rather than counted.
C. It can take on any value within a given range.
D. It includes decimals and fractions in its measurement.
, Answer: A
Conceptual Explanation: Discrete variables are variables for which the values are
countable.
5. In a negatively skewed distribution, which of the following relationships is generally true?
A. Mean > Median > Mode
B. Mean = Median = Mode
C. Mode > Median > Mean
D. Median > Mode > Mean
Answer: C
Conceptual Explanation: In a negatively skewed (left-skewed) distribution, the mean is
pulled toward the tail, making it smaller than the median and mode.
6. According to the Empirical Rule, approximately what percentage of data falls within two
standard deviations of the mean in a bell-shaped distribution?
A. 95%
B. 68%
C. 99.7%
D. 50%
Answer: A
