Stats in Practice

• Part I - Multiple Choice Questions

  The video opens with: "Fewer young people are putting on sunscreen when they are having fun in the sun." They support this conclusion by citing the results of a Center for Disease (CDC) study, in which researchers estimated what value in both 2001 and 2011?

  The average amount of time high-school students spend at the beach. The percentage of high-school students who report they use sunscreen.     The percentage of high-school students who go to the beach. The risk of obesity among children who get fewer than 8 hours of sleep per night.

  Correct. The video opens with a discussion of the percentage of high-school students who report they use sunscreen, indicating that researchers at the CDC estimate that percentage has fallen from 68% in 2001 to 56% in 2011.

  In this CDC study, why is it correct to say that researchers "estimated" a particular population characteristic rather than say the researchers "calculated" that value?

  The researchers did not collect information from any high-school students; instead they just estimated the value based upon their expertise. The researchers could not have measured that population characteristic for all possible high-school students. Instead, they study some high-school students (a "sample") and calculate an estimate for all such students based upon the sample value.    

  Correct. In almost all research studies researchers cannot reach and talk to all members of the target population. The target population in this case is "high-school students." Instead, researchers study some members of the population and estimate the desired value for the population using the sample.
  
  Since the video explicitly says "the data shows," we can be assured that the CDC's estimates are based on research rather than guesses made by experts.

  The video discusses a study conducted by University of Michigan researchers who found that "close community ties can reduce heart attack risk for those over 50." In this study, researchers probably collected a sample of individuals, and for each, measured numerical variables (such as age or weight) as well as categorical variables (such as gender or whether a person has had a heart attack). Which of the following is also a numerical variable that researchers may have measured in this study?

  how many friendly neighbors live within a mile of a person's home whether the person has 0 pets, 1 cat only, 1 dog only, 1 other type of pet only, or more than 1 pet of any type     marital status whether there are friendly neighbors living nearby to help

• Part II - Discussion Question

  The video describes a study that concludes that children who "don't get enough sleep are at a 20% higher risk for obesity." The video says one reason for this association between lack of sleep and obesity might be because those who get less sleep are more fatigued during the day leading to poorer food choices. Describe some other possible explanations for why these two variables might be related.

  
  

  This answer has not been graded yet.

• JMP Applet

  Click here to access the JMP applet in a new window.

• (a)

  There is a fairly strong positive linear relationship between bill amount and tip amount. True or false?

  True False    

• (b)

  Which variable are you trying to predict from a known variable?

  Known variable

  bill amount tip amount    

  Variable to predict

  bill amount tip amount    

• (c)

  As the value of the bill amount increases, does the tip amount increase or decrease?

  increase decrease    

• (d)

  One person paid a bill of $60.72 and tipped $15.00. What sort of tip was the waiter given?

  a very generous one what would be expected     a very miserable one

• (e)

  What is the linear regression equation? (Round your answers to three decimal places.)

  estimated tip amount =

  -0.292

  +

  0.182

  ✕ (bill amount)

Statistical Lab

• Background

  The National Institutes of Health conducts ongoing surveys of US adults called the Health Information National Trends Survey (hereafter abbreviated HINTS).

  From the National Institutes of Health: "The HINTS data collection program was created to monitor changes in the rapidly evolving field of health communication. Survey researchers are using the data to understand how adults 18 years and older use different communication channels, including the Internet, to obtain vital health information for themselves and their loved ones...."

  

  The most recent round of data collection occurred over the course of September 2013–November, 2013 in HINTS 4 Cycle 3. In this lab, you will be using a subset of the HINTS 4 Cycle 3 data to practice creating effective and informative graphical representations of data, which may include histograms and circle graphs.

• About the Data

  For this lab, you need to download the hintsdata.csv dataset. The variables you will be working with are as follows.

  • Age—assume each person's age was rounded to the nearest year; for example, a person in the age
    range [19.5, 20.5)
    would have a reported age of 20, and a person in the
    range [20.5, 21.5)
    would have a reported age of 21, and so on.
  • Gender—the gender of the respondent; categories include 1 = Male and 2 = Female.
  • GeneralHealth—how the respondent rates their overall health; categories include 1 = Excellent, 2 = Very Good, 3 = Good, 4 = Fair, 5 = Poor.

• General Notes

  A few important aspects of creating effective graphical displays of data include the following.

  1. labeling your graphs with descriptive titles
  2. ensuring that the x- and y-axes have appropriate labels
  3. setting the axes to meaningful and/or useful scales

  Your graphs are expected to have these three characteristics.

• Tech Guide

  You will need to use the Excel Tech Guide.

• Lab Questions

  Create a histogram of the variable Age with class intervals 10 years wide. (Submit a file with a maximum size of 1 MB.)

  This answer has not been graded yet.

  Describe the shape of the above histogram.

  The distribution is ---Select--- positively skewed nearly symmetric negatively skewed , centered near ---Select--- 45 55 65 , with ---Select--- little lots of variability.

  Create a circle graph of the variable GeneralHealth. (Submit a file with a maximum size of 1 MB.)

  This answer has not been graded yet.

  Describe how the majority of people in the survey feel about their general state of health.

  The majority of people in the survey feel that their general state of health is ---Select--- excellent or very good good or very good fair or good fair or poor excellent or poor .

  You wish to determine if the age of the respondents who perceive themselves to be in good health differs from the age of the respondents who perceive themselves to be in poor health. Do this by creating two histograms. For the first histogram, plot the variable Age using only the data from respondents who rate their overall health as Excellent, Very Good, or Good. For the second histogram, plot the variable Age using only the data from respondents who rate their overall health as Fair or Poor. Make sure to label your histograms and make sure that they have the same limits for the x-axis, y-axis, and class intervals, so that they can be directly compared. (Submit a file with a maximum size of 1 MB.)

  This answer has not been graded yet.

  Briefly discuss.

  
  

  This answer has not been graded yet.

  Compare how men and women rate their general state of health using a comparative chart. Using your chart, briefly compare and contrast how men and women rate their general state of health.

  
  

  This answer has not been graded yet.

Milestone 1: Research Design

• Question 1

  What is your research question?

  Your research question should be based on a topic that interests you and that you can reasonably obtain data for. Try to make your research question as specific as possible. Form a research question about a population that you will be able to sample. Some examples of research questions are: "Are students at my college able to taste the difference between regular coffee and decaffeinated coffee?", "Does the GPA, age, and number of credits needed for graduation for juniors at my university differ between transfer students and non-transfer students?", "Have the new water rates in my water district changed residents' water usage habits?", and "Do recent graduates from the business department at my university get larger starting salaries on average if they have participated in a summer internship?"

  
  

  This answer has not been graded yet.

• Question 2

  Has any research already been done that might help with your project?

  You can search your university's online database to find articles that discuss research that has already been done on your research question. Please make note of any articles or other sources that helped guide your research question and research design. You will be asked to provide references to any sources you used.

  
  

  This answer has not been graded yet.

• Question 3

  What is your population of interest?

  Your population of interest will be closely related to your research question. For instance, if you are testing the freshman 15 theory and you believe that students at your college do not gain 15 pounds on average over the course of freshman year, then your population of interest is the students at your college who have completed freshman year.

  
  

  This answer has not been graded yet.

• Question 4

  Describe your sampling plan.

  You want to ensure that your sample is representative of the population of interest. How will you target your population of interest? Sampling involves tradeoffs; you may have to settle for a convenience sample, which is fine for this project as long as you acknowledge this. Sampling is about doing the best you can with the resources you have at your disposal.

  
  

  This answer has not been graded yet.

• Question 5

  Will this sample be representative of the population of interest? If so, why? If not, what population will the sample be representative of?

  Is there any group of people within the population of interest that your sampling plan is likely to miss? For instance, if you are using a random sample of landline telephone numbers from your state in order to achieve a random sample of residents in your state, then you are missing all of the residents of your state who only have a cell phone and do not have a landline. Or, if your population of interest is all adults in your country, but you only conduct interview of adults from your local community, then your sample is only representative of the adults in your local community.

  
  

  This answer has not been graded yet.

• Question 6

  What variables will you measure?

  Make sure that the variables you choose are measurable. If you are performing an experiment where you are comparing two skin creams to determine which gives the skin a more youthful glow, how exactly will you measure "youthful glow"? Are there other variables that you will collect because they too may be of interest? Age? Gender? Level of education? Is your variable type numeric or categorical? If your variable type is numeric, is it discrete or continuous? Do your variables need to be measured using special equipment?

  Variable	Type	How will you measure it?
  	---Select--- numeric - discrete numeric - continuous categorical	This answer has not been graded yet.
  	---Select--- numeric - discrete numeric - continuous categorical	This answer has not been graded yet.
  	---Select--- numeric - discrete numeric - continuous categorical	This answer has not been graded yet.
  	---Select--- numeric - discrete numeric - continuous categorical	This answer has not been graded yet.

• Question 7

  Describe your study design.

  Will you be conducting an observational study or performing an experiment? What will your sample size be? If you will be performing an experiment, will there be a placebo? If so, describe the placebo. Will the experiment be blinded? Double-blinded? Who will carry out the experiment and how?

  
  

  This answer has not been graded yet.