Ordinal data and interval data are similar because they can both be ranked in a logical order. However, for interval data, the differences between adjacent scores are equal.
Ordinal data is usually considered qualitative in nature. The data can be numerical, but the differences between categories are not equal or meaningful. This means you can’t use them to calculate measures of central tendency (e.g., mean) or variability (e.g., standard deviation).
Nominal data and ordinal data are similar because they can both be grouped into categories. However, ordinal data can be ranked in a logical order (e.g., low, medium high), whereas nominal data can’t (e.g., male, female, nonbinary).
Data at the nominal level of measurement typically describes categorical or qualitative descriptive information, such as gender, religion, or ethnicity.
Contrary to ordinal data, nominal data doesn’t have an inherent order to it, so you can’t rank the categories in a meaningful order.
Data at the nominal level of measurement is qualitative.
Nominal data is used to identify or classify individuals, objects, or phenomena into distinct categories or groups, but it does not have any inherent numerical value or order.
You can use numerical labels to replace textual labels (e.g., 1 = male, 2 = female, 3 = nonbinary), but these numerical labels are random and are not meaningful. You could rank the labels in any order (e.g., 1 = female, 2 = nonbinary, 3 = male). This means you can’t use these numerical labels for calculations.
A pre-experimental design is a simple research process that happens before the actual experimental design takes place. The goal is to obtain preliminary results to gauge whether the financial and time investment of a true experiment will be worth it.
Pre-experimental design exampleA researcher wants to investigate the effect of a new type of meditation on stress levels in college students. They decide to conduct a small pre-experiment with 10 college students who are already interested in meditation.
The students are asked to participate in a 30-minute meditation session once a week for 4 weeks. The students’ stress levels are measured before and after the meditation sessions with a standardized questionnaire.
The researcher compares the outcomes and notices significant differences in stress scores. They decide to move forward with a more costly and time-consuming experiment where they take into account all criteria for an experimental design (e.g., random assignment of participants, control group, controlling for extraneous variables).
An experimental design diagram is a visual representation of the research design, showing the relationships among the variables, conditions, and participants. It helps researchers to:
Randomization: This principle involves randomly assigning participants to experimental conditions, ensuring that each participant has an equal chance of being assigned to any condition. Randomization helps to eliminate bias and ensures that the sample is representative of the population.
Manipulation: This principle involves deliberately manipulating the independent variable to create different conditions or levels. Manipulation allows researchers to test the effect of the independent variable on the dependent variable.
Control: This principle involves controlling for extraneous or confounding variables that could influence the outcome of the experiment. Control is achieved by holding constant all variables except for the independent variable(s) of interest.
Replication: This principle involves having built-in replications in your experimental design so that outcomes can be compared. A sufficient number of participants should take part in the experiment to make sure that randomization allows for groups with a similar distribution. This increases the chance of detecting true differences.