Question 1

A researcher wants to study the effect of a new fertilizer on tomato plant growth. She randomly assigns 50 plants to receive the fertilizer and 50 plants to receive no fertilizer, then measures the height of each plant after 8 weeks. Which of the following best describes the explanatory and response variables in this experiment?

Accepted Answer

Explanatory variable: fertilizer type; Response variable: plant height

Question 2

Which of the following variables is best classified as a continuous quantitative variable?

Accepted Answer

The temperature of a cup of coffee

Question 3

A survey asks students to rate their agreement with a statement on a scale from 1 (strongly disagree) to 5 (strongly agree). What is the level of measurement for this variable?

Accepted Answer

Ordinal

Question 4

A polling organization selects every 10th person from a list of registered voters to participate in a survey. What type of sampling method is this?

Accepted Answer

Systematic sampling

Question 5

Which of the following best describes the difference between sampling error and non-sampling error?

Accepted Answer

Sampling error is the natural variability from using a sample; non-sampling error is due to mistakes or bias in data collection.

Question 6

A dataset contains the following values: 2, 4, 4, 7, 9. What is the sample mean $$\bar{x}$$?

Accepted Answer

$$\bar{x} = 4.8$$

Question 7

A researcher collects the following data on the number of books read by five students in a month: 1, 3, 3, 5, 9. What is the median $$M$$?

Accepted Answer

$$M = 3$$

Question 8

Given the data set: 2, 4, 4, 7, 9, what is the sample standard deviation $$s$$? (Round to two decimal places)

Accepted Answer

$$s = 2.70$$

Question 9

A student scored 85 on a test where the class mean was 80 and the standard deviation was 5. What is the student's z-score?

Accepted Answer

$$z = 1$$

Question 10

In a boxplot, the median is closer to the lower quartile (Q1) than the upper quartile (Q3), and the right whisker is longer than the left. What can you infer about the distribution?

Accepted Answer

The distribution is skewed right

Question 11

A researcher wants to estimate the average commute time for all employees at a large company. She divides employees into departments and randomly selects 5 employees from each department. What sampling method is she using?

Accepted Answer

Stratified sampling

Question 12

Which of the following is NOT a property of the linear correlation coefficient $$r$$?

Accepted Answer

$$r$$ can be used to prove causation

Question 13

Given the following five-number summary for a dataset: Min = 10, Q1 = 15, Median = 20, Q3 = 25, Max = 40. What is the interquartile range (IQR)?

Accepted Answer

$$IQR = 10$$

Question 14

A study finds a strong positive linear correlation between the number of hours studied and exam scores. Which of the following is a correct interpretation?

Accepted Answer

There is an association between hours studied and exam scores, but causation is not established

Question 15

Given the regression line $$\hat{y} = 2x + 5$$, what is the predicted value when $$x = 4$$?

Accepted Answer

$$\hat{y} = 13$$

Question 16

A researcher uses a convenience sample to survey students in her class about campus dining. Which type of bias is most likely present?

Accepted Answer

Sampling bias

Question 17

A cumulative frequency table shows that the cumulative frequency for the third class is 18, and the total number of observations is 30. What is the cumulative relative frequency for the third class?

Accepted Answer

$$0.60$$

Question 18

Which of the following is an example of a lurking variable in a study examining the relationship between ice cream sales and drowning incidents?

Accepted Answer

The temperature outside

Question 19

A researcher calculates the least-squares regression line for a dataset and finds $$b_1 = 3$ and b_0$ = -2. $$What is the interpretation of $$b_1$$?

Accepted Answer

For each unit increase in $$x$$, the predicted value of $$y$$ increases by 3 units

Question 20

A dataset has a mean of 50 and a standard deviation of 10. An observation is considered an outlier if it is more than 1.5 IQRs above Q3 or below Q1. If Q1 = 40 and Q3 = 60, what is the upper fence for outliers?

Accepted Answer

$$85$$

MA 113: Statistics Midterm 1 Study Guide – Data Collection, Summarizing, and Relationships

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