Question 1

A college administrator wants to estimate the average number of hours per week that all 12,400 students spend studying outside of class. A simple random sample of 250 students is selected, and their average is 8.7 hours. Which of the following best describes the term 'parameter' in this context?

Accepted Answer

The true average number of hours per week that all 12,400 students spend studying.

Question 2

Which of the following variables is quantitative, discrete, and measured at the ratio level?

Accepted Answer

Number of classes taken this semester

Question 3

A university separates students into freshmen, sophomores, juniors, and seniors, then randomly selects 100 students from each group. What sampling method is used?

Accepted Answer

Stratified sampling

Question 4

Researchers randomly assign 120 students to two groups: one uses a new online homework system, the other uses the traditional system. At semester's end, exam scores are compared. Why is random assignment important in this experiment?

Accepted Answer

It helps balance lurking and confounding variables between groups.

Question 5

A college posts a survey link on Instagram and receives 1,200 responses about increasing the student activity fee. 78% oppose the increase. What is the primary source of bias?

Accepted Answer

Voluntary response bias

Question 6

Given the class interval 40-49 minutes in a frequency distribution, what is the class midpoint?

Accepted Answer

$$44.5$$

Question 7

A dataset of waiting times is: 4, 6, 7, 8, 9, 10, 11, 12, 13, 40. Which measure better represents a typical waiting time, and why?

Accepted Answer

Median, because it is resistant to the extreme value of 40.

Question 8

Quiz scores: 62, 70, 74, 76, 80, 84, 88, 90. What is the sample standard deviation? (Round to two decimal places.)

Accepted Answer

$$9.32$$

Question 9

For the ordered dataset: 42, 48, 51, 54, 56, 59, 61, 63, 67, 70, 74, 78, 95, what is the interquartile range (IQR)?

Accepted Answer

$$19.5$$

Question 10

Class A and Class B both have a mean exam score of 78. Class A's standard deviation is $$4.2$$, Class B's is $$12.6. A $$student scores $$90. In $$which class is this score more unusual?

Accepted Answer

Class A, because $$90 is$$ $$2.86$$ standard deviations above the mean.

Question 11

Distribution A: Mean = $$74$$, Median = $$74$$; Distribution B: Mean = $$68$$, Median = $$76$$; Distribution C: Mean = $$84$$, Median = $$77. $$Which distribution is most likely skewed left?

Accepted Answer

Distribution B

Question 12

Why do extreme values usually affect the mean more than the median?

Accepted Answer

The mean is calculated using the numerical magnitude of every observation.

Question 13

A frequency distribution has the following class intervals: 20-29, 30-39, 40-49, 50-59, 60-69, 70-79. If 12 out of 20 students studied less than 50 minutes, what is the percentage?

Accepted Answer

$$60\%$$

Question 14

A newspaper reports average monthly rent increased from $$1,900 in 2025 to$$ $$2,000 in 2026. $$What is the actual percentage increase?

Accepted Answer

$$5.26\%$$

Question 15

Which sampling method involves randomly selecting entire groups and surveying all individuals in those groups?

Accepted Answer

Cluster sampling

Question 16

In a frequency distribution, what is the formula for class midpoint given lower class limit $$L$$ and upper class limit $$U$$?

Accepted Answer

$$\frac{L + U}{2}$$

Question 17

A sample of quiz scores is: 62, 70, 74, 76, 80, 84, 88, 90. What is the sample variance? (Round to two decimal places.)

Accepted Answer

$$86.86$$

Question 18

What is the key difference between stratified sampling and cluster sampling?

Accepted Answer

Stratified sampling selects some individuals from every stratum; cluster sampling randomly selects entire groups and studies all individuals in those groups.

Question 19

If a boxplot's upper whisker extends to $$95$$ and the upper fence is $$101.25$$, what does this indicate?

Accepted Answer

There are no outliers above $$95$$; the whisker extends to the maximum value.

Introductory Statistics Chapters 1 & 2 Study Guidance

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드