Question 1

Which of the following best describes a confounding variable in a statistical study?

Accepted Answer

A variable that is not measured but influences both the independent and dependent variables, potentially distorting the results.

Question 2

In a stem-and-leaf plot, what is the primary purpose of the 'stem'?

Accepted Answer

To organize data into groups based on leading digits, helping visualize the shape and distribution.

Question 3

A researcher wants to study the eating habits of students in a university cafeteria. She selects students who happen to be present at lunchtime. What type of sampling method is this?

Accepted Answer

Convenience sampling

Question 4

Which graph is most appropriate for displaying the frequency of qualitative (categorical) data?

Accepted Answer

Bar graph

Question 5

Given the following data set: 4, 7, 8, 10, 12, 15, 18. What is the interquartile range (IQR)?

Accepted Answer

IQR = $$15 - 8 = 7$$

Question 6

A pie chart is used to represent which type of data?

Accepted Answer

Qualitative (categorical) data

Question 7

If a class interval in a frequency distribution is 10–20, what are the class boundaries?

Accepted Answer

9.5 and 20.5

Question 8

Which sampling method involves dividing the population into subsets based on similar characteristics and then randomly sampling from each subset?

Accepted Answer

Stratified sampling

Question 9

A scatter plot is best used to:

Accepted Answer

Display the relationship between two quantitative variables.

Question 10

In a Pareto chart, categories are arranged:

Accepted Answer

From most to least frequent

Question 11

Which of the following is NOT a characteristic of a histogram?

Accepted Answer

Bars are separated by gaps

Question 12

A researcher wants to compare the test scores of students from two different classes. Which graph would best display this comparison?

Accepted Answer

Bar graph

Question 13

If the mean of a data set is 12, the median is 10, and the mode is 8, what can you infer about the shape of the distribution?

Accepted Answer

The distribution is skewed to the right.

Question 14

Which formula correctly calculates the sample mean $$\bar{x}$$ for a data set with $$n$$ values $$x_1$$, $$x_2$$, ..., x_n$$?

Accepted Answer

$$\bar{x} = \frac{\sum_{i=1}^{n} x_i}{n}$$

Question 15

A frequency polygon is constructed by:

Accepted Answer

Connecting the midpoints of the tops of the bars in a histogram with straight lines.

Question 16

Which of the following best describes blocking in an experimental design?

Accepted Answer

Grouping subjects by similar characteristics to reduce variability.

Question 17

If the 25th percentile of a data set is 8 and the 75th percentile is 15, what is the interquartile range?

Accepted Answer

IQR = $$15 - 8 = 7$$

Question 18

Which of the following is a real-world example of a confounding variable?

Accepted Answer

In a study of exercise and weight loss, diet is not controlled and may affect the results.

Question 19

Which of the following best describes the difference between qualitative and quantitative data?

Accepted Answer

Qualitative data describes categories or characteristics, quantitative data is numerical and measurable.

Question 20

A researcher wants to show the relationship between hours studied and exam scores for a group of students. Which graph should she use?

Accepted Answer

Scatter plot

Descriptive Statistics: Data Organization, Graphs, and Frequency Analysis

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