Dissertations that are based on a quantitative research design attempt to answer at least one quantitative research question. In some cases, these quantitative research questions will be followed by either research hypotheses or null hypotheses. However, this article focuses solely on quantitative research questions. Furthermore, since there is more than one type of quantitative research question that you can attempt to answer in a dissertation (i.e., descriptive research questions, comparative research questions and relationship-based research questions), we discuss each of these in this article. If you do not know much about quantitative research and quantitative research questions at this stage, we would recommend that you first read the article, Quantitative research questions: What do I have to think about, as well as an overview article on types of variables, which will help to familiarise you with terms such as dependent and independent variable, as well as categorical and continuous variables [see the article: Types of variables]. The purpose of this article is to introduce you to the three different types of quantitative research question (i.e., descriptive, comparative and relationship-based research questions) so that you can understand what type(s) of quantitative research question you want to create in your dissertation. Each of these types of quantitative research question is discussed in turn:
Descriptive research questions simply aim to describe the variables you are measuring. When we use the word describe, we mean that these research questions aim to quantify the variables you are interested in. Think of research questions that start with words such as "How much?", "How often?", "What percentage?", and "What proportion?", but also sometimes questions starting "What is?" and "What are?". Often, descriptive research questions focus on only one variable and one group, but they can include multiple variables and groups. We provide some examples below:
| Question: | How many calories do Americans consume per day? |
| Variable: | Daily calorific intake |
| Group: | Americans |
| Question: | How many calories do American men and women consume per day? |
| Variable: | Daily calorific intake |
| Group: | 1. American men 2. American women |
| Question: | How often do British university students use Facebook each week? |
| Variable: | Weekly Facebook usage |
| Group: | British university students |
| Question: | How often do male and female British university students upload photos and comment on other users' photos on Facebook each week? |
| Variable: | 1. Weekly photo uploads on Facebook 2. Weekly comments on other users? photos on Facebook |
| Group: | 1. Male, British university students 2. Female, British university students |
| Question: | What are the most important factors that influence the career choices of Australian university students? |
| Variable: | Factors influencing career choices |
| Group: | Australian university students |
In each of these example descriptive research questions, we are quantifying the variables we are interested in. However, the units that we used to quantify these variables will differ depending on what is being measured. For example, in the questions above, we are interested in frequencies (also known as counts), such as the number of calories, photos uploaded, or comments on other users? photos. In the case of the final question, What are the most important factors that influence the career choices of Australian university students?, we are interested in the number of times each factor (e.g., salary and benefits, career prospects, physical working conditions, etc.) was ranked on a scale of 1 to 10 (with 1 = least important and 10 = most important). We may then choose to examine this data by presenting the frequencies, as well as using a measure of central tendency and a measure of spread [see the section on Data Analysis to learn more about these and other statistical tests].
However, it is also common when using descriptive research questions to measure percentages and proportions, so we have included some example descriptive research questions below that illustrate this.
| Question: | What percentage of American men and women exceed their daily calorific allowance? |
| Variable: | Daily calorific intake |
| Group: | 1. American men 2. American women |
| Question: | What proportion of British male and female university students use the top 5 social networks? |
| Variable: | Use of top 5 social networks (i.e. Facebook, MySpace, Twitter, LinkedIn, and Classmates) |
| Group: | 1. Male, British university students 2. Female, British university students |
In terms of the first descriptive research question about daily calorific intake, we are not necessarily interested in frequencies, or using a measure of central tendency or measure of spread, but instead want understand what percentage of American men and women exceed their daily calorific allowance. In this respect, this descriptive research question differs from the earlier question that asked: How many calories do American men and women consume per day? Whilst this question simply wants to measure the total number of calories (i.e., the How many calories part that starts the question); in this case, the question aims to measure excess; that is, what percentage of these two groups (i.e., American men and American women) exceed their daily calorific allowance, which is different for males (around 2500 calories per day) and females (around 2000 calories per day).
If you are performing a piece of descriptive, quantitative research for your dissertation, you are likely to need to set quite a number of descriptive research questions. However, if you are using an experimental or quasi-experimental research design, or a more involved relationship-based research design, you are more likely to use just one or two descriptive research questions as a means to providing background to the topic you are studying, helping to give additional context for comparative research questions and/or relationship-based research questions that follow.
Comparative research questions aim to examine the differences between two or more groups on one or more dependent variables (although often just a single dependent variable). Such questions typically start by asking "What is the difference in?" a particular dependent variable (e.g., daily calorific intake) between two or more groups (e.g., American men and American women). Examples of comparative research questions include:
| Question: | What is the difference in the daily calorific intake of American men and women? |
| Dependent variable: | Daily calorific intake |
| Groups: | 1. American men 2. American women |
| Question: | What is the difference in the weekly photo uploads on Facebook between British male and female university students? |
| Dependent variable: | Weekly photo uploads on Facebook |
| Groups: | 1. Male, British university students 2. Female, British university students |
| Question: | What are the differences in usage behaviour on Facebook between British male and female university students? |
| Dependent variable: | Usage behaviour on Facebook (e.g. logins, weekly photo uploads, status changes, commenting on other users' photos, app usage, etc.) |
| Group: | 1. Male, British university students 2. Female, British university students |
| Question: | What are the differences in perceptions towards Internet banking security between adolescents and pensioners? |
| Dependent variable: | Perceptions towards Internet banking security |
| Groups: | 1. Adolescents 2. Pensioners |
| Question: | What are the differences in attitudes towards music piracy when pirated music is freely distributed or purchased? |
| Dependent variable: | Attitudes towards music piracy |
| Groups: | 1. Freely distributed pirated music 2. Purchased pirated music |
Groups reflect different categories of the independent variable you are measuring (e.g., American men and women = "gender"; Australian undergraduate and graduate students = "educational level"; pirated music that is freely distributed and pirated music that is purchased = "method of illegal music acquisition").
Comparative research questions also differ in terms of their relative complexity, by which we are referring to how many items/measures make up the dependent variable or how many dependent variables are investigated. Indeed, the examples highlight the difference between very simple comparative research questions where the dependent variable involves just a single measure/item (e.g., daily calorific intake) and potentially more complex questions where the dependent variable is made up of multiple items (e.g., Facebook usage behaviour including a wide range of items, such as logins, weekly photo uploads, status changes, etc.); or where each of these items should be written out as dependent variables.
Overall, whilst the dependent variable(s) highlight what you are interested in studying (e.g., attitudes towards music piracy, perceptions towards Internet banking security), comparative research questions are particularly appropriate if your dissertation aims to examine the differences between two or more groups (e.g., men and women, adolescents and pensioners, managers and non-managers, etc.).
Whilst we refer to this type of quantitative research question as a relationship-based research question, the word relationship should be treated simply as a useful way of describing the fact that these types of quantitative research question are interested in the causal relationships, associations, trends and/or interactions amongst two or more variables on one or more groups. We have to be careful when using the word relationship because in statistics, it refers to a particular type of research design, namely experimental research designs where it is possible to measure the cause and effect between two or more variables; that is, it is possible to say that variable A (e.g., study time) was responsible for an increase in variable B (e.g., exam scores). However, at the undergraduate and even master's level, dissertations rarely involve experimental research designs, but rather quasi-experimental and relationship-based research designs [see the section on Quantitative research designs]. This means that you cannot often find causal relationships between variables, but only associations or trends.
However, when we write a relationship-based research question, we do not have to make this distinction between causal relationships, associations, trends and interactions (i.e., it is just something that you should keep in the back of your mind). Instead, we typically start a relationship-based quantitative research question, "What is the relationship?", usually followed by the words, "between or amongst", then list the independent variables (e.g., gender) and dependent variables (e.g., attitudes towards music piracy), "amongst or between" the group(s) you are focusing on. Examples of relationship-based research questions are:
| Question: | What is the relationship between gender and attitudes towards music piracy amongst adolescents? |
| Dependent variable: | Attitudes towards music piracy |
| Independent variable: | Gender |
| Group: | Adolescents |
| Question: | What is the relationship between study time and exam scores amongst university students? |
| Dependent variable: | Exam scores |
| Independent variable: | Study time |
| Group: | University students |
| Question: | What is the relationship amongst career prospects, salary and benefits, and physical working conditions on job satisfaction between managers and non-managers? |
| Dependent variable: | Job satisfaction |
| Independent variable: | 1. Career prospects 2. Salary and benefits 3. Physical working conditions |
| Group: | 1. Managers 2. Non-managers |
As the examples above highlight, relationship-based research questions are appropriate to set when we are interested in the relationship, association, trend, or interaction between one or more dependent (e.g., exam scores) and independent (e.g., study time) variables, whether on one or more groups (e.g., university students).
The quantitative research design that we select subsequently determines whether we look for relationships, associations, trends or interactions. To learn how to structure (i.e., write out) each of these three types of quantitative research question (i.e., descriptive, comparative, relationship-based research questions), see the article: How to structure quantitative research questions.