Classifying variables as independent or dependent:

The independent variable is the one being manipulated or grouped in the study for comparison. A tip to remember this is to think that independent starts with “I” and I, the researcher, manipulate that variable or have control over who is grouped in the study. The way we will be using independent variables in this course is in terms of between group analysis, so our focus will be on groups being compared. Note that the participants are not the independent variable! Rather, the independent variable is the concept by which you group the participants.

*Do not forget to include the levels (groups) for the independent variable when you type up your lab answers. The levels are the groups being compared.

The dependent variable is the outcome, the variable on which the groups are being compared. This variable is measured for all participants.

Example: If the goal was to compare Caucasian to African Americans to see whether they differ on salary, ethnicity is the independent variable, with Caucasian and African Americans being the two IV groups. Salary is the dependent variable.

Measurement scales (modified from Cozby, 2013)

This classification system categorizes the variables as being measured on a nominal, ordinal, interval, or ratio scale. A variable’s measurement scale has implications for the types of statistical analysis used; certain statistical tests are appropriate for certain measurement scales. As such, classifying variables correctly is a necessary step before one can run the appropriate statistical tests. You will have to classify variables in subsequent labs as well as for your research project, so it is important to master these concepts. Here is a reminder of the scales:

Nominal: There is no relative ordering of the levels for the variable; the different levels are simply different from each other but not in order. In other words, the levels reflect different categories of the variable, but there is no order to them. The assignment of numeric scores to each level (e.g., 1 for Caucasian, 2 for African American) is arbitrary. For example, in terms of ethnicity: Caucasian is not more, higher, better, less, lower, or worse than African American. It is simply a different category than African American.

Ordinal: There is an order to the levels, but the distance between the levels is unknown because you assigned values to the different levels given the variable’s levels are not already in quantified form. The assignment of values to the levels is somewhat arbitrary and meaningless, and there is no way to know whether the difference is equal between levels. Again, you assign numbers to the various levels, but the numbers are meaningless and somewhat arbitrary. For example, you may assign 1-5 to the levels, and you know that 5 is more or higher than the lower levels, but you do not know whether the magnitude of difference between level 5 and 4 is the same as between 4 and 3.

Interval: The variable’s levels are in quantified form. As such, there is an order to the levels, which is meaningful, and the distance between levels is equal over all levels of the scale. However, there is no absolute or true zero point. For example, the difference between level 1 and 2 is the same as between 2 and 3, but there is no true zero point. NOTE that the textbook mentions extraversion as a personality measure that could be an example of interval. Personality measures are NOT true interval variables, but researchers in social sciences may argue that some measures of psychological concepts have been standardized and as such, those measures can be considered interval. They are not true interval variables, but classifying them as such allows researchers to use more advanced statistical analysis. For this course and assignment, we are using the true definition of interval variable as described in this paragraph. Psychological measures for which values are arbitrarily assigned are ordinal, not interval!

Ratio: This is similar to interval in that the distance between levels is meaningful and equal over all levels of the scale, but there is also a fixed and true zero point. If you are measuring a variable and there is equal distance between the levels, think about whether it makes sense that there is a true 0 point for the variables. Ask yourself could the variable cease to exist if the value was 0. If so, the variable would be ratio.

Many students find these concepts confusing, so take your time Although the categories are not listed for the variables in the measurement scales section of the lab, there is enough information there for you to determine its measurement scale.

Independent vs Dependent Variables (1.5 points each = IV is worth 1 point, DV is worth .5 point)

For each of the following four descriptions of studies, identify the independent and dependent variables. When typing in your answers, follow the example below. For the independent variable, be sure to include in parentheses the groups being compared.

Example: Students watched a cartoon either alone or with others and then rated how funny they found the cartoon to be.

            IV: Cartoon (alone and others)

            DV: Funniness

An adolescent egocentrism questionnaire was given to male and female college students.

IV:

DV:

Women suffering from PMS volunteered to participate in a study about a drug to alleviate the symptoms of PMS. The women were randomly spilt: half received the drug and the other half received a placebo. Severity of PMS symptoms was recorded during their next premenstrual cycle.

IV:

DV:

After watching a love movie or a horror movie, a romanticism questionnaire was given to a group of adults.

IV:

DV:

Parents were classified into the type of parenting style (e.g., authoritative, authoritarian, or permissive) they use. The parents were asked to rate their perception of how much discipline they use with their children.

IV:

DV:

Measurements of Scale (1 point each)

For each the following descriptions of variables, identify whether a nominal, ordinal, interval, or ratio scale is being used.

Example: An item measuring Ethnic group categories of people in a neighborhood, with options being White, Black, Hispanic, or Asian. = nominal

A check box item measuring gender, with male or female as options. =

An item measuring the wife’s household income, with income filled in the blank. =

Items measuring self-esteem on a disagree to agree scale. =

An item where preschool children participants must check their favorite color, with blue, red, yellow, green, purple, or pink as options. =

An item measuring number of times a preschooler says the word “love,” with the number filled in the blank. =

An item measuring the parenting style of teen mothers, with authoritative, authoritarian, uninvolved, or permissive as options. =

An item measuring the high temperature on each day of the week, with temperature filled in the blank. =

A check box item measuring the religious affiliation of the Presidents of the United States, with Christian, Jewish, Mormon, Islam, or Muslim as options. =

An item measuring the math SAT scores of Sand Creek High School seniors, with options ranging continuously from 200-800. =

An item measuring the social competence score for adolescents who spend more than 3 hours per day on social networking sites, with options ranging from low competence to high competence. =