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Eighty-three healthy volunteers, aged 65 to 85, who ate fewer than 2 servings of fruits and vegetables per day, participated in a study. The participants were randomly assigned to one of two groups. One group was instructed to continue with their normal diet for sixteen weeks. The other group was instructed to included 5 or more portions of fruits and vegetables per day as part of their normal diet for the same sixteen weeks.  This is an example of which study design?

Existing data of biological attributes for alligators, such as snout length in inches and weight in pounds, can be used as indicators of restoration success in water quality. Suppose the weight is converted from pound to kilogram (1 kilogram  =  2.2 pounds approximately), the correlation  coefficient, r, between the height and length will

Researchers studying psychological stress have several variables they can use to measure stress.  Which one of the following variables is categorical?

The graph below shows per capita soft drink consumption versus median income, for the 48 contiguous U. S. states and the District of Columbia (Source: American Community Survey).                 What is a plausible value for the correlation between soft drink consumption and state median income?  

A researcher studied 500 pregnant American women throughout their pregnancies and recorded the amount of weight they gained, the weight of their newborn babies, whether or not they smoked, and how often they exercised. Which of the following is a categorical variable?

A statistics instructor creates a student survey to get to know her students.  She created the survey from questions students provided.  Select ALL graphs that could be used to summarize the following survey question:  What state are you from?

The World Health Organization collected data on obesity in 182 countries around the world.  The following graph shows the percent people who are “overweight or obese,” where the individuals have been grouped into separate categories according to their country’s income level.                   Which one statement below best describes the graph?

The following dot plot shows the number of books read last semester by a group of 20 students.      Which of the following describes the shape of the distribution?

The New England Journal of Medicine reported that people who suffer a cardiac arrest in public places like casinos have a higher survival rate than those who have a heart attack in a hospital.  Which one of the following is a valid interpretation of this finding?

Lake Superior has ice for a long period each winter.   Below is some data and a scatterplot of the number of days ice was present at one of the stations on Lake Superior versus the mean temperature for the months of December through April, for nine seasons (1966-67 through 1974-75).                         The least squares regression line fit to this data is Days of Ice = 253.0 – 6.254 x Mean Temperature.   with r-squared = 57.1%.  Which of the following is the correct interpretation of r-squared?