2.2: Part One- The Scientific Method
All rigorous scientific inquiry follows the scientific method. Understanding this process is essential when devising and carrying out your own experiments and critically analyzing the results of other experiments. T here are two types of scientific inquiry: discovery-based and hypothesis-based. Discovery-based science is often exploratory or descriptive, whereas hypothesis-based inquiry is used to answer ‘how’ and ‘why’ questions. Hypothesis-based science follows the steps scientific method.
The scientific method is a systematic process that scientists use to gather information and test their ideas about the world. It typically involves the following steps:
- Observing and asking questions: Scientists observe the natural world and ask questions about what they observe with their senses. Both types of scientific inquiry use this.
- Forming a hypothesis: A hypothesis is a testable explanation for the observations, it is NOT an educated guess. Scientists form a hypothesis based on their observations and background knowledge.
- Designing an experiment: Scientists design an experiment to test their hypothesis. They must control all other variables so that they can isolate the effects of the variable they are studying.
- Collecting data: Scientists collect data by performing their experiments. They measure and record the results. Being able to measure something is a key component of science. Scientists have invented and developed many tools to aid in making measurements with a high degree of accuracy and measuring things that are impossible to measure with just human senses.
- Analyzing data: Scientists analyze their data to see if it supports or disproves their hypothesis. They look for patterns and relationships in their data.
- Drawing conclusions: Based on the data, scientists draw conclusions about the validity of their hypothesis. If the data support the hypothesis, scientists must form a new hypothesis and start the process over again.
- Communicating results: Scientists communicate their results to others through publications, conferences, and other means. Other scientists can then attempt to replicate the results to verify their validity.
To write a good hypothesis , first answer your question: is it ‘yes’, or ‘no’? Then, explain why you think this is the answer. Then write this into a clear statement. For example, you may suspect that the abundance of birds is related to the number of trees. You think this is because more trees = more food and nesting sites:
‘Bird abundance increases with the number of trees in a habitat because more trees increase the amount of food and nesting sites.’
You must explain HOW bird abundance varies with tree density. A mediocre hypothesis would be ‘bird density changes with tree density’ because it doesn’t address how it may happen and doesn’t account for increases or decreases. Another example that could use improvement might be: ‘the number of leaves in a forest positively correlates to bird abundance’ because it doesn’t try to explain why that happens not to mention that it would be extremely difficult to make an experiment to test this.
Test your understanding: hypothesis
You notice that your dog prefers chicken to vegetables. Research tells you that dogs were selectively bred from wolves: efficient predators with a meat-based diet.
Write a hypothesis for this observation:
Make a prediction . There are many ways to test your hypothesis. You could count the number of birds you see in an hour; you could count the number of nests or feathers you find; put out bird feeders and count how much food is eaten per bird visit… likewise, there are many ways of counting the number of trees.
Your prediction is what you think you will see in the ACTUAL RESULT(S) that you will collect in YOUR experiment if your hypothesis is not proven wrong . It also helps to restate the hypothesis in your prediction:
Example predictions:
If your methods were to walk in a forest and observe the number of birds seen in a day and then count all of the trees, your prediction would be: ‘if bird density increases with tree density then more birds will be counted in one day in habitats with more trees compared to habitats with fewer trees.’
If instead you put out bird feeders and used the amount of food eaten to indicate how many birds there are, your prediction would be: ‘if bird density increases with tree density then more food will be eaten from bird feeders in habitats with more trees compared to habitats with fewer trees.’
Test your understanding: Prediction
You test whether dogs prefer chicken to vegetables by giving dogs two bowls of food: one with 200g of chicken, the other with 200g of boiled vegetables. After 1 minute you record how much food is left in each bowl.
Write a prediction for this experiment based on the hypothesis you wrote earlier:
Carry out an experiment . Use accurate and precise methods that enable you to collect unbiased, accurate data and test your hypothesis. A variable is anything that can be measured or controlled in an experiment. An independent variable is a variable that you will manipulate. The dependent variable is the variable being tested and that often ‘depends’ i.e. responds to the independent variable. In our example, we think that the number of birds depends on the number of trees. The independent variable is the number of trees and the dependent variable is the number of birds .
A control variable is something that is kept constant, such as temperature, or the type of binoculars you use to observe birds. A control group is a group in which you will compare your experimental group with. For example, if you wanted to test the impact of eating sugar on tooth decay, your control group will be the group not given extra sugar, whereas the experimental group is given extra sugar.
Only test one variable at a time! Otherwise, you will not be able to see what is impacting your dependent variable. If we tested both tree density and insect abundance at the same time, we would not know which one was affecting bird density.
Test your understanding: variables
Identify the independent and dependent variables for your experiment testing food preferences in dogs:
Independent:
Dependent:
7. Form a conclusion . What did you find? What does your data show? What is the answer to your question? Your conclusion is always based on your results and analyses and states whether your hypothesis and predictions were supported. Remember: it is ok to not support your hypothesis or to not reach a concrete conclusion! This is all part of the scientific process. If your hypothesis is disproven, go back and formulate and test a new one! This is often the time when you would write your entire experiment into a lab report.
6. Analyze your data. You now need to examine and analyze your findings to find out what they mean. This could be as simple as plotting a graph of your results or calculating means and ranges. The method you chose should reveal the answer to your question. For our example, we could plot a graph of the number of trees vs. the number of birds in an area.