1.2 Homework
Determine whether the study depicts an observational study or an experiment. A poll is conducted by a school's English department in which second-grade students are asked if they prefer to be in their English class or their science class.
The study is an observational study because the study examines individuals in a sample comma but does not try to influence the response variable.
(a) What does it mean when an observational study is retrospective? (b) What does it mean when an observational study is prospective?
(a) A retrospective study requires that individuals look back in time or require the researcher to look at existing records. (b) A prospective study collects the data over time.
Determine whether the study depicts an observational study or an experiment. Sixty patients with vision loss are divided into two groups. One group is treated with experimental surgery. The other is not. After one month, both groups are questioned about their ability to read.
The study is an experiment because the researchers control one variable to determine the effect on the response variable.
(a) What is an observational study? (b) What is a designed experiment? (c) Which allows the researcher to claim causation between an explanatory variable and a response variable?
(a) An observational study measures the value of the response variable without attempting to influence the value of either the response or explanatory variables. (b) A designed experiment is when a researcher assigns individuals to a certain group, intentionally changing the value of an explanatory variable, and then recording the value of the response variable for each group. (c) designed experiment.
(a) Explain what is meant by confounding. (b) What is a lurking variable? (c) What is a confounding variable?
(a) Confounding in a study 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 response variable may be due to some other variable or variables not accounted for in the study. (b) A lurking variable is an explanatory variable that was not considered in a study, but that affects the value of the response variable in the study. In addition, lurking variables are typically related to explanatory variables in the study. (c) A confounding variable is an explanatory variable that was considered in a study whose effect cannot be distinguished from a second explanatory variable in the study.
(a) What is a cross-sectional study? (b) What is a case-control study? (c) Which is the superior observational study? Why?
(a) Cross-sectional studies are observational studies that collect information about individuals at a specific point in time or over a very short period of time. (b) Case-control studies are observational studies that are retrospective, meaning that they require individuals to look back in time or require the researcher to look at existing records. (c) Neither study is always the superior to the other. Both have advantages and disadvantages that depend on the situation.
Researchers wanted to determine if having a DVD player in the bedroom is associated with obesity. The researchers administered a questionnaire to 365 twelve-year-old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a DVD player in their bedroom was significantly higher than that of the adolescents who did not have a DVD player in their bedroom. Complete parts (a) through (e) below (a) Why is this an observational study? What type of observational study is this? (b) What is the response variable in the study? Is the response variable qualitative or quantitative? What is the explanatory variable? (c) Can you think of any lurking variables that may affect the results of the study? (d) In the report, the researchers stated, "These results remain significant after adjustment for socioeconomic status." What does this mean? (e) Does a DVD player in the bedroom cause a higher body mass index? Explain.
(a) The researchers administered a questionnaire to obtain their data without trying to influence an explanatory variable of the study. Cross-sectional study. (b) The response variable is the body mass index of the adolescents. The response variable is quantitative. The explanatory variable is whether the adolescent has a DVD player in the bedroom or not. (c) Yes. For example, possible lurking variables might be eating habits and the amount of exercise per week. (d) It means that socioeconomic status is not an explanatory variable and that including this variable in the study does not change the results of the study. (e) No. It can only be said that a DVD player in the bedroom and obesity are associated because the body mass index of adolescents who had a DVD player in their bedroom was significantly higher than that of adolescents who did not have a DVD player in their bedroom.
Researchers wanted to determine if having a television (TV) in the bedroom is associated with obesity. The researchers administered a questionnaire to 376 twelve-year-old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom. (a) Why is this an observational study? What type of observational study is this? (b) What is the response variable in the study? Is the response variable qualitative or quantitative? What is the explanatory variable? (c) Can you think of any lurking variables that may affect the results of the study? (d) In the report, the researchers stated, "These results remain significant after adjustment for socioeconomic status." What does this mean? (e) Does a television in the bedroom cause a higher body mass index? Explain.
(a) The researchers administered a questionnaire to obtain their data without trying to influence an explanatory variable of the study. Cross-sectional study. (b) The response variable is the body mass index of the adolescents. The response variable is quantitative. The explanatory variable is whether the adolescent has a TV in the bedroom or not. Yes. For example, possible lurking variables might be eating habits and the amount of exercise per week. (d) The researchers made an effort to avoid confounding by accounting for potential lurking variables. (e) No. It can only be said that a TV in the bedroom and obesity are associated because the body mass index of the adolescents who had a TV in their bedroom was significantly higher than that of the adolescents who did not have a TV in their bedroom.
Researchers wanted to determine if having a cushioned desk chair in the bedroom is associated with obesity. The researchers administered a questionnaire to 389 twelve-year-old adolescents. After analyzing the results, the researchers determined that the body mass index of the adolescents who had a cushioned desk chair in their bedroom was significantly higher than that of the adolescents who did not have a cushioned desk chair in their bedroom. (a) Why is this an observational study? What type of observational study is this? (b) What is the response variable in the study? Is the response variable qualitative or quantitative? What is the explanatory variable? (c) Can you think of any lurking variables that may affect the results of the study? (d) In the report, the researchers stated, "These results remain significant after adjustment for socioeconomic status." What does this mean? (e) Does a cushioned desk chair in the bedroom cause a high body mass index? Explain.
(a) The researchers administered a questionnaire to obtain their data without trying to influence an explanatory variable of the study. This observational study is a cross-sectional study. (b) The response variable is the body mass index of the adolescents. The response variable is quantitative. The explanatory variable is whether the adolescent has a cushioned desk chair in the bedroom or not. (c) Yes. For example, possible lurking variables might be eating habits and the amount of exercise per week. (d) The researchers made an effort to avoid confounding by accounting for potential lurking variables. (e) No. It can only be said that a cushioned desk chair in the bedroom and obesity are associated because the body mass index of the adolescents who had a cushioned desk chair in their bedroom was significantly higher than that of the adolescents who did not have a cushioned desk chair in their bedroom.
Researchers wanted to determine if there was an association between the level of satisfaction of an individual and their risk of lung cancer. The researchers studied 1851 people over the course of 7 years. During this 7-year period, they interviewed the individuals and asked questions about their daily lives and the hassles they face. In addition, hypothetical scenarios were presented to determine how each individual would handle the situation. These interviews were videotaped and studied to assess the emotions of the individuals. The researchers also determined which individuals in the study experienced any type of lung cancer over the 7-year period. After their analysis, the researchers concluded that the satisfied individuals were less likely to experience lung cancer. (a) what type of observation study was this? (b) What is the response variable? What is the explanatory variable? (c) In the report, the researchers stated that "the research team also hasn't ruled out that a common factor like genetics could be causing both the emotions and the lung cancer." Explain what this sentence means.
(a) This was a _cohort study_ because the information collected about a group of individuals _by observing them over a long period of time_. (b) The response variable is _whether or not lung cancer is contracted,_ because it _is the variable of interest_. / The explanatory variable is _the level of satisfaction_ because it _affects the other variable_. (c) The researchers may not be concerned with cofounding that occurs when the effects of two or more explanatory variable are not separated or when there are some explanatory variables that were not considered in a study, but that affect the value of the response variable.
Researchers wanted to determine if there was an association between the level of happiness of an individual and their risk of high blood pressure. The researchers studied 1785 people over the course of 13 years. During this 13-year period, they interviewed the individuals and asked questions about their daily lives and the hassles they face. In addition, hypothetical scenarios were presented to determine how each individual would handle the situation. These interviews were videotaped and studied to assess the emotions of the individuals. The researchers also determined which individuals in the study experienced any type of high blood pressure over the 13-year period. After their analysis, the researchers concluded that the happy individuals were less likely to experience high blood pressure. Complete parts (a) through (c). (a) What type of observational study was this? Explain. (b) What is the response variable? (c) In the report, the researchers stated that "the research team also hasn't ruled out that a common factor like genetics could be causing both the emotions and the high blood pressure." Explain what this sentence means. Choose the correct answer below.
(a) This was a _cohort study_, because information was collected about a group of individuals _by observing them over a long period of time_. (b) This response variable is _whether or not high blood pressure was contracted,_ because it _is the variable of interest_. The explanatory variable is _level of happiness_, because it _affects the other variable_. (c) The researchers may be concerned with confounding that occurs when the effects of two or more explanatory variables are not separated or when there are some explanatory variables that were not considered in a study, but that affect the value of the response variable.
Determine whether the study depicts an observational study or an experiment. Athletes are randomly divided into two groups. One group trains using weight resistance; the other trains using cardio. After 2 months, each group completes a fitness test to compare agility.
The study is an experiment because the researchers control one variable to determine the effect on the response variable.
Determine whether the study depicts an observational study or an experiment. Fifty patients with colon cancer are divided into two groups. One group receives an experimental drug to fight cancer, the other a placebo. After one year, the spread of the cancer is measured.
The study is an experimental because the researchers control one variable to determine the effect on the response variable.
Determine whether the study depicts an observational study or an experiment. A study is conducted to determine if there is a relationship between heart arrhythmias and caffeine consumption. A sample of 100 people with a heart arrhythmia are asked about their caffeine consumption.
The study is an observational study because the study examines individuals in a sample comma but does not try to influence the response variable.
Determine whether the study depicts an observational study or an experiment. A study is conducted to determine if there is a relationship between skin cancer and hair color. The hair color of patients with skin cancer is recorded.
The study is an observational study because the study examines individuals in the sample, but does not try to influence the response variable.
Determine whether the study depicts an observational study or an experiment. Eighth-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 its proficiency with that of the other group.
The study is experimental because the researchers control one variable to determine the effect on the response variable.