Section 1.2 Handout

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Mathematics

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Jun 26, 2024

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Math 1342 Dr. Tarcia Hubert Name: __Eytravia Franklin__ Section 1.2 – Observational Studies Versus Designed Experiments “It does not matter how slowly you go as long as you do not stop.” ~Confucius Video 1: Observational Study vs Designed Experiment Key Terms: • ____ Explanatory Variable ____ - The variables that can be altered or manipulated in research, or the variable used to explain or predict differences in the response variable. • ____ Response Variable ____ - The outcome that is predicted or measured following manipulation of the explanatory variables. Example: A researcher wants to assess the risk associated with smoking cigarettes by looking at a group of people, determining how many are smokers, and comparing the rate of lung cancer of the smokers to the nonsmokers. Explanatory Variable – Smoking of cigarettes (smokers vs nonsmokers) Response Variable – Rate of lung cancer ___ Observational Study ___ - measures the value of the response variable without attempting to influence the value of either the response or explanatory variables. Advantages: Lower cost, greater timeliness, broader range of patients Disadvantage: Can’t claim causation only association More Key Terms: __ Confounding __ - occurs when the effects of two or more explanatory variables are not separated. Therefore, any relation that may exist between an explanatory variable and the

Math 1342 Dr. Tarcia Hubert Name: __Eytravia Franklin__ response variable may be due to some other variable or variables not accounted for in the study. __ Confounding Variables __ - an explanatory variable that was considered in a study whose effect cannot be distinguished from a second explanatory variable in the study. __ Lurking Variables __ - an explanatory variable that was not considered in a study, but that affects the value of the response variable in the study. Example: A professor wanted to conduct an experiment to study the effects of homework type on student success. The professor used online homework with her morning class, and traditional textbook homework with her afternoon class. At the end of the semester, she compared the final exam scores from the online homework section to those of the traditional homework section. If the morning class had higher exam scores, can the professor conclude that the higher scores were due to the online homework? - No __ Designed Experiment __ - when a researcher assigns the individuals in a study to a certain group, intentionally changes the value of the explanatory variable, and then records the value of the response variable for each group. Advantage – Allows identification of certain cause-and-effect relationships among variables. Disadvantages – Take longer and can be costly Example 1: Is the following study an observational study or designed experiment? • The American Cancer Society is beginning a study to learn why some people never get cancer. To take part in the study, a person must be 30-65 years of age and never had cancer. The study requires that the participants fill out surveys about their health and habits and give blood samples and waist measurements. These surveys must be filled out every two years. The study is expected to last for the next 20 years. - Observational Study Example 2: Is the following study an observational study or designed experiment?

Math 1342 Dr. Tarcia Hubert Name: __Eytravia Franklin__ • Rats with cancer are divided into two groups. One group receives 5 milligrams (mg) of a medication that is thought to fight cancer, and the other receives 10 mg. After 2 years, the spread of the cancer is measured. - Designed Experiment Example 3: Is the following study an observational study or designed experiment? • A survey is conducted asking 400 people, “Do you prefer Coke or Pepsi?” - Observational Survey Example 4: Is the following study an observational study or designed experiment? • Seventh grade students are randomly divided into two groups. One group is taught math using traditional techniques; the other is taught math using a reform method. After 1 year, each group is given an achievement test to compare proficiency. - Designed Experiment Video 2: Types of Observational Studies __ Cross-sectional Studies __ - Observational studies that collect information about individuals at a specific point in time, or over a very short period of time. Advantage – Cheap and fast Disadvantage – May not get the full picture __ Case-control Studies ___ - These studies are retrospective , meaning that they require individuals to look back in time or require the researcher to look at existing records. In case- control studies, individuals who have certain characteristics are matched with those that do not. Advantage – Cheap and fast Disadvantage – Requires people to recall information and people to tell the truth

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Math 1342 Dr. Tarcia Hubert Name: __Eytravia Franklin__ ___ Cohort Studies ___ - identifies a group of individuals to participate in the study (the cohort). The cohort is then observed over a long period of time. Over this time period, characteristics about the individuals are recorded. Because the data is collected over time, cohort studies are prospective . Advantage – The most powerful of the observational studies Disadvantage – Individuals tend to drop out due to the long period of time Example: Is a television in a bedroom associated with obesity? Researchers questioned 379 twelve-year-old adolescents and concluded that the body mass index (BMI) of the adolescents who had a TV in their room was significantly higher than the BMI of those who did not have a TV in their bedroom. • What type of observational study is this? - Cross-sectional • What is the response variable? - BMI measurement • What is the explanatory variable? - TV in the room or not • Can you think of any lurking variables? - Amount of exercise per week, eating habits, family history, how much time you watch tv, etc. • Can we conclude that having a television in the room causes higher BMI? Explain. - No, can’t make causation claims with observation studies, we can only claim association __ Census __ - a list of all individuals in a population along with certain characteristics of each individual. __ Web Scraping or Data Mining __ - is the process of extracting data from the Internet.

Section 1.2 Handout

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