Stats Semester 1 Exam Review

What is the purpose of the random assignment of treatments to subjects in an experiment?

• To create roughly equivalent groups before treatments are administered.

• To prevent certain groups in the population from being systematically excluded in the experiment.

• To reduce bias in the selection of the subjects to be included in the experiment.

• To eliminate the need for blinding in an experiment.

A random number generator is used to select 12 students from a large statistics class to rate a statistics video. The 12 students selected are

• the population

• a simple random sample of the class

• a census

• a voluntary response sample

A recent study showed that teenagers who had night lights in their rooms as babies are more likely to suffer from myopia (near sightedness) than teenagers who had not used night lights. But genetic factors are known to play a role, and near-sighted parents are more likely to install a night light in their children’s room. This makes it hard to tell if the night light caused the myopia. This is an example of

• double-blinding.

• the placebo effect.

• a confounding variable.

• an explanatory variable.

Which of the following is a valid statistical question?

• How many people voted in the last school board election?

• How many points were scored by the New England Patriots during the 2014-15 regular NFL season?

• How long will you be in line when your get lunch from the cafeteria?

• How tall is Mount Everest?

The most important advantage of experiments over observational studies is that

• experiments are usually easier to carry out.

• experiments can give better evidence of causation.

• confounding cannot happen in experiments.

• an observational study cannot have a response variable

At the beginning of the school year, a high-school teacher asks every student in her classes to fill out a survey that asks for their age, gender, the number of years they have lived at their current address, their favorite school subject, and whether they plan to go to college after high school. Which of the following best describes the types of variables that are being measured?

• five quantitative variables.

• two categorical variables and two quantitative variables.

• two categorical variables and three quantitative variables.

• three categorical variables and two quantitative variables.

Steve’s boss told him that he did not deserve a raise and that Steve was making an amount similar to other managers with his experience. Steve gathered some data and found that the z-score for his salary as compared to other managers with the same level of experience is -1.35. Which of the following is the best interpretation of this z-score?

• Steve makes 1.35% less than other managers with his experience level.

• Steve makes $1.35 less per pay period than the average for managers with his experience level.

• Steve makes $1.35 less per hour than the average for managers with his experience level.

• Steve’s salary is 1.35 standard deviations below the mean salary of all managers with his experience level.

Which of the following are resistant to outliers?

• The mean and standard deviation.

• The median and standard deviation.

• The median and the IQR.

• The range and the IQR.

The five-number summary of the distribution of scores on the final exam in Psych 001 last semester was [min =18, Q1 = 39, Med = 62, Q3 = 76, Max = 100]. A total of 416 students took the exam. About how many students had scores above 39?

• 104

• 208

• 312

• 400

Which of the distributions has the larger standard deviation?

• Distribution A

• Distribution B

• They are equal because they have the same range

• They are equal since both distributions are symmetric