**What Is A Research (Scientific) Hypothesis?**

A plain-language explainer + examples

By: Derek Jansen (MBA) | Reviewed By: Dr Eunice Rautenbach | June 2020

If you’re new to the world of research, or it’s your first time writing a dissertation or thesis, you’re probably noticing that the words “research hypothesis” and “scientific hypothesis” are used quite a bit, and you’re wondering **what they mean in a research context**.

“Hypothesis” is one of those words that people use loosely, thinking they understand what it means. However, it has a **very specific meaning** within academic research. So, it’s important to understand the exact meaning before you start hypothesizing.

**What is a hypothesis?**

Let’s start with the general definition of a hypothesis (not a research hypothesis or scientific hypothesis), according to the Cambridge Dictionary:

*Hypothesis: an idea or explanation for something that is based on known facts but has not yet been proved.*

In other words, it’s a statement that provides an **explanation** for why or how something works, based on **facts** (or some reasonable assumptions), but that has **not yet been specifically tested**. For example, a hypothesis might look something like this:

*Hypothesis: sleep impacts academic performance.*

This statement **predicts** that academic performance will be influenced by the amount and/or quality of sleep a student engages in – sounds reasonable, right? It’s based on **reasonable** **assumptions**, underpinned by what we currently know about sleep and health (from the existing literature). So, loosely speaking, we could call it a hypothesis, at least by the dictionary definition.

**But that’s not good enough…**

Unfortunately, that’s not quite **sophisticated enough** to describe a research hypothesis (also sometimes called a scientific hypothesis), and it wouldn’t be acceptable in a dissertation, thesis or research paper. In the world of academic research, a statement needs a few more criteria to constitute a true **research hypothesis**.

**What is a research hypothesis?**

A research hypothesis (also called a scientific hypothesis) is a statement about the expected outcome of a study (for example, a dissertation or thesis). To constitute a quality hypothesis, the statement needs to have three attributes – **specificity**, **clarity** and **testability****. **

Let’s take a look at these more closely.

**Hypothesis Essential #1: Specificity & Clarity**

A good research hypothesis needs to be **extremely clear and articulate** about both **what’**s being assessed (who or what variables are involved) and the **expected outcome** (for example, a difference between groups, a relationship between variables, etc.).

Let’s stick with our sleepy students example and look at how this statement could be more specific and clear.

*Hypothesis: Students who sleep at least 8 hours per night will, on average, achieve higher grades in standardised tests than students who sleep less than 8 hours a night.*

As you can see, the statement is very specific as it identifies the **variables** **involved** (sleep hours and test grades), the **parties** **involved** (two groups of students), as well as the **predicted** **relationship** type (a positive relationship). There’s no ambiguity or uncertainty about who or what is involved in the statement, and the expected outcome is clear.

Contrast that to the original hypothesis we looked at – *“Sleep impacts academic performance”* – and you can see the difference. “Sleep” and “academic performance” are both comparatively **vague**, and there’s no indication of what the expected **relationship** **direction** is (more sleep or less sleep). As you can see, specificity and clarity are key.

**Hypothesis Essential #2: Testability (Provability)**

A statement must be **testable** to qualify as a research hypothesis. In other words, there needs to be **a way to prove** (or disprove) the statement. If it’s not testable, it’s not a hypothesis – simple as that.

For example, consider the hypothesis we mentioned earlier:

*Hypothesis: Students who sleep at least 8 hours per night will, on average, achieve higher grades in standardised tests than students who sleep less than 8 hours a night.*

We could test this statement by undertaking a **quantitative study** involving **two groups** of students, one that gets 8 or more hours of sleep per night for a fixed period, and one that gets less. We could then **compare** the standardised test results for both groups to see if there’s a statistically significant difference.

Again, if you compare this to the original hypothesis we looked at – *“Sleep impacts academic performance”* – you can see that it would be quite difficult to test that statement, primarily because it isn’t specific enough. How much sleep? By who? What type of academic performance?

So, remember the mantra – if you can’t test it, it’s not a hypothesis 🙂

**Defining A Research Hypothesis**

You’re still with us? Great! Let’s recap and pin down a clear definition of a hypothesis.

*A research hypothesis (or scientific hypothesis) is a statement about an expected relationship between variables, or explanation of an occurrence, that is clear, specific and testable.*

So, when you write up hypotheses for your dissertation or thesis, make sure that they meet all these criteria. If you do, you’ll not only have rock-solid hypotheses but you’ll also ensure a clear focus for your entire research project.

**What about the null hypothesis?**

You may have also heard the terms **null hypothesis**, alternative hypothesis, or **H-zero** thrown around. At a simple level, the null hypothesis is the **counter-proposal** to the original hypothesis.

For example, if the hypothesis predicts that there **is a relationship** between two variables (for example, sleep and academic performance), the null hypothesis would predict that there is **no relationship** between those variables.

At a more technical level, the null hypothesis proposes that **no statistical significance** exists in a set of given observations and that any differences are due to chance alone.

**And there you have it – hypotheses in a nutshell. **

If you have any questions, be sure to leave a comment below and we’ll do our best to help you. If you need hands-on help developing and testing your hypotheses, consider our private coaching service, where we hold your hand through the research journey.

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In a book I read a distinction is made between null, research, and alternative hypothesis.

As far as I understand, alternative and research hypotheses are the same.

Can you please elaborate?

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Afshin

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Very good definition. How can I cite your definition in my thesis? Thank you. Is nul hypothesis compulsory in a research?

It’s a counter-proposal to be proven as a rejection

Please what is the difference between alternate hypothesis and research hypothesis?

It is a very good explanation. However, it limits hypotheses to statistically tasteable ideas. What about for qualitative researches or other researches that involve quantitative data that don’t need statistical tests?

In qualitative research, one typically uses propositions, not hypotheses.

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Excellent. Thanks for being clear and sound about the research methodology and hypothesis (quantitative research)

I have only a simple question regarding the null hypothesis.

– Is the null hypothesis (Ho) known as the reversible hypothesis of the alternative hypothesis (H1?

– How to test it in academic research?

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