HW 1.2

Lurking variable

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. A relation that appears to exist between a certain explanatory variable and the response variable may be due to some other variable or variables not term-1accounted for in the study. These variables are called lurking variables.

What does it mean when an observational study is​ prospective?

A prospective study collects the data over time.

What does it mean when an observational study is​ retrospective? A. A retrospective study requires that individuals look back in time or require the researcher to look at existing records. B. A retrospective study is a list of all individuals in a population along with certain characteristics of each individual. C. A retrospective study collects the data over time.

A retrospective study requires that individuals look back in time or require the researcher to look at existing records.

What do you hope to determine in research?

In research we wish to determine how varying the amount of an explanatory variable affects the value of a response variable

What are the two methods for collecting data?

Observational studies and designed experiments

Confounding variable

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. The big difference between lurking variables and confounding variables is that lurking variables are not considered in the study whereas confounding variables are measured in the study.

What is a designed experiment?

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.

What is an observational​ study?

An observational study measures the value of the response variable without attempting to influence the value of either the response or explanatory variables.

Confounding

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. Confounding is potentially a major problem with observational studies.​ Often, the cause of confounding is a lurking variable.

Determine whether the study depicts an observational study or an experiment. Fourth-grade students are randomly divided into two groups. One group is taught English using traditional techniques. The other is taught English 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 an experiment because the researchers control one variable to determine the effect on the response variable.

What should be done after a research question is developed?

You must develop methods for obtaining the data that can be used to answer the questions posed in the research objective

Researchers wanted to determine if there was an association between daily kale consumption and the occurrence of breast cancer. The researchers looked at 93,062 women and asked them to report their kale​-eating habits. The researchers also determined which of the women had IDC breast cancer. After their​ analysis, the researchers concluded that consumption of two or more servings of kale per day was associated with a reduction in IDC breast cancer. Complete parts​ (a) through​ (c) below. ​(a) What type of observational study was​ this? Explain. (b) What is the response variable in the​ study? Is the response variable qualitative or​ quantitative? (c) What is the explanatory​ variable? (d) In their​ report, the researchers stated that​ "After adjusting for various demographic and lifestyle​ variables, daily consumption of two or more servings was associated with a​ 30% reduced prevalence of IDC breast cancer​." Why was it important to adjust for these​ variables?

(a) This was a​ cross-sectional study because all information about the individuals was collected at a specific point in time. (b) The response variable is whether the woman has IDC breast cancer or not. The response variable is qualitative. (c) The explanatory variable is consumption of Kale (d) 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.

Which allows the researcher to claim causation between an explanatory variable and a response​ variable?

A designed experiment

What is a response variable

Also known as the dependent or outcome variable, its value is predicted or its variation is explained by the explanatory variable; in an experimental study, this is the outcome that is measured following manipulation of the explanatory variable

What is an explanatory variable?

Also known as the independent or predictor variable, it explains variations in the response variable; in an experimental study, it is manipulated by the researcher

Which is the superior observational​ study? Why? Choose the correct answer below. A. Neither study is always the superior to the other. Both have advantages and disadvantages that depend on the situation. B. Cross-sectional studies are always the superior observational study because they are cheap and quick to do. C. Case-control studies are always the superior observational study because they are relatively inexpensive to conduct and can be done relatively quickly.

Neither study is always the superior to the other. Both have advantages and disadvantages that depend on the situation. Both studies are inexpensive and can be done relatively quickly. A​ case-control study is limited in that it requires individuals to recall information​ correctly, and to answer questions truthfully. A​ cross-sectional study is limited in that it only gives information at a specific point in time or over a very short period of​ time, and might not contain valuable information that occurs outside of that point in time.

Determine whether the study depicts an observational study or an experiment. Forty people are divided into two groups. One group is exposed to atonal classical music. The other is not. After one month​, both groups are questioned about their ability to remember random phrases.

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. A study is conducted to determine if there is a relationship between hearing loss and exposure to mumps. One thousand patients with hearing loss are asked about their exposure to mumps.

The study is an observational study because the study examines individuals in a sample but does not try to influence the response variable.

Determine whether the study depicts an observational study or an experiment. A poll is conducted by a school's math department in which sixth-grade students are asked if they prefer to be in their math class or their English class.

The study is an observational study because the study examines individuals in a sample, but does not try to influence the response variable.

What is a​ case-control study?

​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. In​ case-control studies, individuals that have a certain characteristic are matched with those that do not. A disadvantage to this type of study is that it requires individuals to recall information from the past. Plus it requires the individuals to be truthful in their responses. An advantage of​ case-control studies is that they are relatively inexpensive to conduct and can be done relatively quickly.

What is a​ cross-sectional study?

​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. For​ example, a researcher might want to assess the risk associated with smoking by looking at a group of​ people, determining how many are smokers and comparing the incidence rate of lung cancer of the smokers to the nonsmokers. A clear advantage of​ cross-sectional studies is that they are cheap and quick to do.​ However, cross-sectional studies have limitations. For the lung cancer​ study, it could be that individuals develop cancer after the data are​ collected, so the study will not give the full picture.