Experimental Design Year 10 Science

What is Experimental design? What are the “rules” for designing an experiment? As a class discuss the following questions: 1. Is there a specific way to design an experiment? 2. Are their rules scientists follow when designing an experiment? 3. Are all experiments designed in the same way? 4. What kinds of experiments have you done on your own? Some ideas you may like to discuss are: cooking, testing sports techniques, trying to fix things, etc.

Rules for designing an experiment: Decide what you want to investigate – that is what are you testing in your experiment? Decide how you are going to measure the effect of what you are testing. This may be measured in numbers or observations. Choose a title that describes the effect or thing you are investigating. How do you know that the test results would not happen anyway? Control? How do you make sure the only thing that has an effect on the measurement is the thing you are testing? Is testing it once enough? Repeats? Write a statement that describes what you want to do, this is your Aim MAKE HYPOTHESIS. This is an educated guess or a prediction about the outcome of the experiment. Hypothesis must be stated in a way that can be tested by an experiment. Make a list of the things you need to do the experiments, and prepare them. Make a step-by-step list of what you will do to answer your questions. This list is called an experimental procedure or method.

Rules for designing an experiment continued: Make a step-by-step list of what you will do to answer your questions. This list is called an experimental procedure or method. Do the experiment and record all numerical measurements or observations made Summarize what happened. This could be in the form of a table of numerical data or graphs. It could also be a written statement of what occurred during the experiments and may include drawings. Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Could the design of the experiment be improved? This is the discussion. Make a brief sentence of how the experiment addressed your aim. This component is your conclusion WHAT IF MY SCIENCE PROJECT DOESN'T WORK? No matter what happens, you will learn something. Science is not only about getting "the answer." Knowing that something didn't work, is actually knowing quite a lot. Experiments that don't turn out as planned are an important step in finding an answer.

Explore worksheet Using the Explore worksheet, found on Moodle, you are to read the description of an experiment and answer questions about its design.

Experimental design in science Watch the YouTube clip https://www.youtube.com/watch?v=7q8acfBx5to (8.41min)

Understanding the Different Types of Variables There are two types of variables: quantitative and qualitative. It is important to recognize which type(s) of variables you are evaluating, as some calculations and statistical tests can only be performed on data containing one or the other type of variable. Quantitative variables are ones that differ in magnitude. They can easily be measured and recorded as a number. Examples of quantitative variables include - age - height - time and - weight. Quantitative variables are easy to summarize using numerical calculations like median and average.

Qualitative variables, sometimes referred to as categorical variables, are ones where the observations differ in kind. Qualitative variables can be placed in categories like: gender (male vs. female) or marital status (unmarried, married, divorced, widowed). This makes them particularly good for summarizing as percentages in a pie or bar chart. Sometimes, qualitative data can be ranked. For example, a fruit survey might rank the taste of the fruit as: 1 = Very sweet 2 = Moderately sweet 3 = Slightly sweet 4 = Neither detectably sweet nor sour 5 = Slightly sour 6 = Moderately sour 7 = Very sour

Vocabulary / glossary terms Independent variable the part of the experiment that is controlled or changed by the experimenter Dependent variable the part of the experiment that is observed or measured to gather data; changes because of the independent variable Control standard of comparison in the experiment; level of the independent variable that is left in the natural state, unchanged Constant part of the experiment that is kept the same to avoid affecting the dependent variable Hypothesis educated guess or prediction about an experiment’s results Qualitative observation descriptive observations such as color or texture Quantitative observation measurable observations Inference the act of reasoning from factual knowledge or evidence

Scientific Variables https://www.youtube.com/watch?v=K078eJ9Jsx4 (20 minutes)

Scientific variables Watch the YouTube clips: Scientific variables by Alex Koning (8.25 minutes) https://www.youtube.com/watch?v=nzfDvfoBv_g Control and variable groups (2.18 minutes) https://www.youtube.com/watch?v=aLesk8fujH8 How to identify independent and dependant variables (12.15 Minutes) https://www.youtube.com/watch?v=JjYT4IK4jEs

Examples of variables in Scientific experiments.. If a scientist conducts an experiment to test the theory that a vitamin could extend a person’s life-expectancy, then: •The independent variable is the amount of vitamin that is given to the subjects within the experiment. This is controlled by the experimenting scientist. •The dependent variable, or the variable being affected by the independent variable, is life span.

Try for yourself Experiment 1 How do the different chemicals in fertilisers affect plant growth? Independent variable: Different chemicals in fertilisers Dependant variables: plant growth Experiment 2: How long does it take three different types of enzymes each individually to digest a litre of milk? Independent variable: type of enzyme Dependant variable: time taken to digest milk Experiment 3: What is the effect of the density of different mediums (eg. Air and glass) on the speed at which light travels? Independent variable: density of different mediums Dependant variable: speed at which light travels

Explain worksheet Using the Explain worksheet, found on Moodle, you are to read the description of an experiment and answer questions about its design.

Think- pair- Share As a class we are going to do the Pepsi-Coke Challenge. The question or scientific problem we are going to answer is: Can girls taste the difference between Pepsi and Coke better than boys? In pairs think about how you might test this. Think about what would be your independent and dependant variables, what would be the control, what would be your constant etc ? As a class discuss the best method for setting up the experiment.

Go to Moodle Download the: 1. Pepsi Coke experimental design graphic organizer 2. Pepsi Coke Result table and Data analysis sheet

You need to think about the sorts of data you may need record You need to think about the sorts of data you may need record. Things like age, frequency of drinking soda (daily, weekly, monthly, rarely), ability to roll tongue, or anything else they think might be interested in, the results can be analyzed for each variable. Using the Pepsi Coke Result table and Data analysis sheet (on Moodle), complete the experiment and analyse the data. You are to make a bar graph of your results listing each variable with the percent correct and discuss the reliability of the results. Does gender actually affect your ability to taste?

If you were going to design an experiment to test the following what sorts of thing would you need to consider? Investigate the effects of colour on plant growth Investigate flower colour and insect attraction

Student Design Experiment You are now going choose one of the topics from the list. You will then design and conduct an experiment in groups of two to three to test your chosen topic. You need to ensure you think about all of the things we have previously discussed.

Project ideas for Student Designed Experiment.. To test the effect of music on memory and whether or not listening to music affects the ability of a person to concentrate on a simple task. Does caffeine enhance athletic performance • Does the colour of food or drinks affect whether or not we like them? • Which paper towel brand is the strongest or the most absorbent? • Does the colour of hair affect how much static electricity it can carry? (test with balloons) • What is the effect of salt on the boiling temperature of water? Which brand of nappy holds the most liquid?

Project ideas for Student Designed Experiment... Continued... Which type of cup will keep a hot drink warm longer: paper, plastic, Styrofoam, or glass? How does the temperature of a tennis ball affect the height of its bounce? A comparative study of the strength of fishing line Compare the strength of different coloured hair Compare various window cleaning techniques Investigate the effectiveness of stain removal products Compare the volume of carbon dioxide produced by fizzy antacid tablets

Scientific method planning Before you are able to conduct your experiment you need to ensure you have thought carefully about all the variables involved. What equipment you will need and the procedure you will use to obtain your results. Download the Scientific Method Planning Booklet from Moodle and fill it in. Once you have had your Plan approved by your teacher and your equipment has been ordered, you are then able to begin experimental testing.