Which keyword most likely indicates data from a population?

A researcher records the weights (in kilograms) of dogs at an animal shelter: $7$, $12$, $9$, $15$, $11$, $8$, $14$, $10$, $13$, $16$. Are these data qualitative or quantitative, and what is the level of measurement? Provide your reasoning.

In a city poll, residents were asked, "Do you recycle regularly?" The poll results reported that $65.2\%$ of respondents said yes. Is the statement "$65.2\%$ of residents polled recycle regularly" descriptive or inferential?

Which of the following best describes the statistical concept of confounding in observational studies?

A health magazine conducted an online survey asking, “Should people reduce their daily sugar intake?”

Of the 1320 respondents who chose to participate, 78% answered “yes”. Is the value of 78% a statistic or a parameter?

A study of laptop ergonomics assigned $200$ office workers to use either an external keyboard or the laptop keyboard for $1$ workweek and switched the keyboard type the following week (randomized order). For each week, the researchers recorded the average number of wrist movements per minute during typing. What is the response variable? Is it qualitative or quantitative?

A study investigates the effect of three different toothpaste brands (P, Q, R) and water on plaque removal. $72$ artificial teeth are randomly assigned to one of four treatments: toothpaste P, toothpaste Q, toothpaste R, or water. Each tooth is brushed in a mechanical device for $10$ minutes, repeated four times (for a total of $40$ minutes). The researcher measuring the plaque removal is blinded to the treatment methods. The percentage of plaque removed is recorded. Researchers found that P and Q removed more plaque than R or water. State a factor that could affect the response variable that is fixed at a set level.

Find the regression equation, letting the first variable be the predictor (x) variable. Then determine the indicated predicted value. Use the data from 10 hair salon visits listed below. Suppose the appointment time is 75 minutes. How does the predicted tip compare to the actual tip of \$12.50?

According to the least-squares principle, the regression line is the one that makes the sum of squared residuals as small as possible. Refer to the dinner duration data in the table below and use the regression equation.

$\hat{y}=1.10+0.102x$

Identify the 10 residuals by comparing the actual tip to the predicted tip for each observation.

In a study of 987 high school students performed by a research group, participants were asked how frequently they wear seat belts while riding in a car. 75% of respondents said "always".

Identify the sample and the population in the study.

Which of the following best describes a placebo in a clinical trial?

A study reports that regular consumption of brewed coffee is associated with a lower risk of heart disease, and the authors add, "These associations persisted after adjustment for cigarette smoking." What does this statement mean?

a. The investigators removed all smokers from the data, so the result applies only to non-smokers.

b. The investigators included cigarette smoking as a control variable, so the effect of coffee is estimated while holding smoking constant.

c. The investigators ignored smoking because it had no relation to either coffee consumption or heart disease.

d. The investigators proved smoking is not a cause of heart disease by adjusting for it.

A survey was conducted among $1,200$ residents of a city to determine their satisfaction with the public transportation services. The survey found that $68\%$ of the respondents were satisfied with their services. Which part of this survey represents the descriptive branch of statistics? What conclusions might be drawn from the survey using inferential statistics?

Identify the population, sample, and the sample data set.

A poll of $300$ households in a city found that $20\%$ planned to install solar panels within the next year.

Researchers want to study the effects of different exercise routines on muscle strength. To conduct the experiment, they recruit $120$ volunteers and plan to assign them to one of three groups, including a control group. How can they design this experiment using a completely randomized design?