Description
Week 1 Assignment: Evidence, Claims and Study Types
Week  Assignments  Due Date 
Week 1  Introduction Forum (Not graded by required) 
Suggested Due Date: Wednesday of Week 1 
Graded Discussion  Suggested Due Date—
Initial Post: Wednesday of Week 1
Due Date— Responses: Sunday of Week 1 [Have two posts on two different days] 

Knewton Homework Assignments
Evidence, Claims and Study Types (Section 1.4) Variable and Measures of Data (Section 1.3) Sampling Methods (Section 1.2) Comparing Sampling Methods (Section 1.2) 
Sunday of Week 1 
Objectives
1.1 Evidence, Claims and Study Types
 Identify and describe the steps in the statistical analysis process
 Determine whether a study is observational or an experiment and appropriate use cases
 Identify components of the experimental design in a given experiment: use of a control group, use of a placebo, and blinding
Activity 1
Question
A researcher is interested in the effects of watching videos just before bed on the quality of sleep. He has decided to test the claim that “Watching 1 hour of video just before going to bed reduces the number of minutes of REM sleep by more than 10%.” How should the number of hours of video be treated?
Activity 2
Question
Identify and describe the steps in the statistical analysis process
The goal of statistics is to use data to understand something about the world. To obtain useful results, a scientific approach should be followed. The basic approach can be summarized in a few steps.
 Write a question that can be answered by collecting data.
 Determine what variables to measure and how to collect a data sample.
 Analyze the data and create appropriate summaries.
 Create a report of the results, drawing conclusions or inferences where appropriate.
For example, suppose you are the owner of a small business that helps local farmers sell their produce at grocery stores in a city. The farmers are interested in knowing what crops they should produce and look to you to help provide some guidance. This type of question can be better understood using statistical analysis. The four steps of the statistical process are described in general and then applied to this situation in the table below.
Write a question
Writing a question or claim involves identifying the group of items or individuals of interest, or the population. Then, you must determine what kind of information about that population is important.
The group of interest is the people living in the city who shop for food at grocery stores. To help the farmers, you need to answer the question “What kinds of produce do those people buy and in what amounts?”
Determine what variables to measure and how to collect the data
Variables are properties or attributes of the individuals in the population that can be measured. To obtain data, a sample of the population must be chosen and the variables that are important to the situation should be recorded for each individual in the sample.
It is important that the sample be representative of the population and that it not be subject to bias. Bias is introduced when some part of the population is over or underrepresented.
To answer the question, the variables should include the amounts of each kind of produce being purchased.
An appropriate sampling method would be to go to each of the grocery stores in the city and survey a random sample of the people making purchases at the store.
Since the growing season is limited to a particular time of year, the survey should be conducted during a time when the crops would be available from the farmers.
Analyze the data
Analysis of the data involves calculating appropriate summaries for the variables. For numeric variables, this includes calculating averages and typical ranges for the variable. For other variables, the summaries may involve charts of the distribution of the values.
Since the quantity of produce purchased is a numeric variable, it would be appropriate to create summaries of the average amounts and their ranges. It would also be helpful to the farmers to see the relative percentages of each kind of produce, so charts showing the distribution of different kinds of produce should be created.
Draw conclusions
When a sample is randomly selected without bias, then it should be representative of the population. For reasonably large sample sizes, the results should be generalizable to the population.
The sampling method here used randomly selected shoppers at the stores in the city, so the result should be representative of the population. The results should be generalizable to all shoppers.
Evaluate the sampling method
Question
When collecting the data, you choose a Saturday morning and send a person to each of the five stores in the city. You have them use a die to choose the people to interview by rolling the die each time a person leaves the store and only interviewing a person if the roll is a 1. Will this method produce a random sample that is representative of the population?
Activity 3
Question
A statistics student is doing a project for her class. She wants to make a prediction for the outcome of an upcoming national election. Since there are only two candidates, she decides that her question is “Which candidate do more people favor in the upcoming election?” She decides to randomly interview 100 students crossing the courtyard on campus about their preference. Is this sample good for drawing general conclusions about the results of the election?
Activity 4
Question
In the description of the following experiment, determine the experimental factor. A pharmaceutical company conducted an experiment to test a breakfast drink for school children. The company enrolled students for the experiment in the age group of 6 to 10 and divided them into two groups. One group received the new breakfast drink with their normal breakfast, and the other group drank the same amount of a similarlooking juice. Identify the experimental factor.
Activity 5
Question
A candy manufacturer is interested in the distribution of colors in each of its packages of candy sold. What should the researchers do first?
Activity 6
Question
A researcher wants to find out the effect of the amount of protein eaten at breakfast on the aerobic performance of runners. Would an experimental or observational study design be more appropriate?
Activity 7
Question
In the description of the following experiment, determine the experimental factor.
A research team is testing a product that will minimize wrinkles among older adults. Volunteers in the age group of 40 to 45 are included in the research. The research team gives a cream to be applied on the face to one group and a placebo cream to the other group.
Activity 8
Question
A scientist is interested in finding out the effect of soil quality on crop yield. Would an experimental or observational study design be more appropriate?
Activity 9
Question
A researcher is interested in the effects of watching videos just before bed on the quality of sleep. He has decided to test the claim that “Watching 1 hour of video just before going to bed reduces the number of minutes of REM sleep by more than 10%. ” Which of the following data collection processes would be appropriate? Select only one answer choice.
Activity 10
Question
A consumer research company is interested in determining if a certain company’s new refrigerator model is more efficient than the older model. Researchers decided to investigate the claim that the new model uses 10% less electricity than the older model for the same cooling load. To collect data, the company obtains 20 random refrigerators for each model. They are all placed in one building well separated from each other and are loaded with 50 bottles of water. The electricity usage is monitored for one month. How can the results be generalized?
Activity 11
Question
A researcher wants to evaluate the effect of using Facebook on happiness. Would an experimental or observational study design be more appropriate?
Activity 12
Question
A researcher is interested in seeing if there is a relationship between the use of a particular software program and age of the user. The researcher conducts a survey of adults in which she categorizes the respondents into one of two categories, either 18−35years old, or 35 years and older.
Is the study described observational or experimental? If it is an experiment, what is the controlled factor?
Activity 13
Question
In the description of the following experiment, determine the experimental factor. During a study testing a new vaccine drug for the Zika virus, the research team grouped the volunteers enrolled for the test into Group A and Group B. Group A received an inert drug (placebo) while Group B received the vaccine drug.
Activity 14
Question
In the description of the following experiment, determine the experimental factor. A research team is testing a paste form of a drug to alleviate inflammation. Participants are grouped into Team A and Team B. Team A receives the paste form of the drug. Team B receives a similar paste with no active ingredients.
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