Q: Using the Empirical Rule, if the population mean is $$29.8$$ and the population standard deviation is $$6.4$$, about 95% of commute times should lie between which two values?

$$29.8 - 2 \times 6.4 = 17.0$$ and $$29.8 + 2 \times 6.4 = 42.6$$

Q: If the five-number summary for commute times is: minimum $$=18$$, $$Q_1=25$, median =30.5$, Q_3$=35$$, maximum $$=40$$, what is the lower fence for outliers?

$$Q_1 - 1.5$$ \times IQR = 25 - 1.5 \times 10 = 10$$

Question 1

A nutritionist conducts a study to determine if a new diet reduces cholesterol. She selects 80 participants and measures their cholesterol before and after the diet. Which of the following best describes the population in this study?

Accepted Answer

All individuals who follow the new diet worldwide

Question 2

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

Accepted Answer

Number of pets owned

Question 3

A researcher collects survey responses from college students about daily screen time and GPA. Which variable is the explanatory variable?

Accepted Answer

Daily screen time

Question 4

A company surveys only employees at headquarters about remote work. What type of bias is most likely present?

Accepted Answer

Sampling bias

Question 5

In a survey of 200 households, 40 prefer shopping as their favorite weekend activity. What is the relative frequency for shopping?

Accepted Answer

$$0.20$$

Question 6

Given the frequency distribution of quiz scores for 40 students, what is the class width for the intervals 40–49, 50–59, 60–69, 70–79, 80–89?

Accepted Answer

$$10$$

Question 7

Which distribution shape best describes salaries at a company where a few executives earn millions while most employees earn much less?

Accepted Answer

Skewed right

Question 8

Given the commute times: 18, 22, 25, 28, 30, 31, 33, 35, 36, 40, what is the population mean?

Accepted Answer

$$29.8$$

Question 9

Suppose the sample is the first five commute times: 18, 22, 25, 28, 30. What is the sample mean?

Accepted Answer

$$24.6$$

Question 10

For the commute times data, what is the interquartile range (IQR) if $$Q_1 = 25$, Q_3$ = 35$$?

Accepted Answer

$$10$$

Question 11

Using the Empirical Rule, if the population mean is $$29.8$$ and the population standard deviation is $$6.4$$, about 95% of commute times should lie between which two values?

Accepted Answer

$$29.8 - 2 	imes 6.4 = 17.0$$ and $$29.8 + 2 	imes 6.4 = 42.6$$

Question 12

If the five-number summary for commute times is: minimum $$=18$$, $$Q_1=25$, median =30.5$, Q_3$=35$$, maximum $$=40$$, what is the lower fence for outliers?

Accepted Answer

$$Q_1 - 1.5$$ 	imes IQR = 25 - 1.5 	imes 10 = 10$$

Question 13

Which of the following best describes the level of measurement for the variable 'Ranking of the top 5 tennis players'?

Accepted Answer

Ordinal

Question 14

A survey about remote work is sent to all employees, but only 20% respond, mostly those unhappy with remote work. What type of bias is most likely present?

Accepted Answer

Nonresponse bias

Question 15

If a variable is measured as temperature in Fahrenheit, which level of measurement does it represent?

Accepted Answer

Interval

Question 16

In a frequency distribution, which class has the highest frequency if the frequencies are: 4, 6, 10, 12, 8?

Accepted Answer

70–79

Question 17

If the mean commute time is $$29.8$$ and the median is $$30.5$$, what can you infer about the shape of the distribution?

Accepted Answer

Approximately symmetric

Question 18

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

Accepted Answer

It describes a characteristic of a population

Question 19

A study finds that the average drop in cholesterol among 80 participants is 15 points. What is this value called?

Accepted Answer

Statistic

STA2023 Practice Midterm 1: Step-by-Step Statistics Guidance

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