How Science Works Identifying Variables and Designing Investigations

Identifying variables and Designing Investigations Learning outcomes: By the end of the lesson you should be able to Explain what the different types of variables are. Recognise different variables in example experiments. Understand why the consideration of variables is important when designing an experiment.

The INDEPENDENT VARIABLE Also known as the INPUT variable. This is the thing that you change or manipulate, the thing you are testing.

The DEPENDENT VARIABLE Also known as the OUTPUT variable. This is the thing that you measure or observe, it’s the results of the experiment. –Y–You expect the dependent variable to be affected by the independent variable.

The CONTROL VARIABLES Any variable that you keep the same in order to allow for a ‘fair test’.

7 September, 2015 Identifying variables and Designing Investigations Example No. 1 A student thinks that year 10 students will be better at doing a quiz than year 8 students. –T–T–T–Task 1: Write down the independent, dependent and control variables in this experiment.

7 September, 2015 Identifying variables and Designing Investigations Example No. 1 Independent variable = the year group the students are in (year 10 or year 8) Dependent variable = the students scores on the quiz Control variables = the same quiz should be used, students should have the same amount of time to complete it.

7 September, 2015 Identifying variables and Designing Investigations Example No. 2 A student has made the following prediction for an experiment; “the more caffeine I drink the quicker my reaction times will be.” –T–T–T–Task 2: What are the independent, dependent and control variables in this experiment.

7 September, 2015 Identifying variables and Designing Investigations Example No. 2 Independent variable = the amount of caffeine drunk by the student (e.g. number of cups of cola) Dependent variable = the students reaction times (e.g. how quick they can catch a ruler) Control variables = the same type of drink, same method of measuring reaction time.

7 September, 2015 Identifying variables and Designing Investigations Example No. 3 The light intensity was measured at different points moving away from the trunk of a large tree in full leaf. –T–T–T–Task 3: What are the independent, dependent and control variables in this experiment.

7 September, 2015 Identifying variables and Designing Investigations Example No. 3 Independent variable = the distance from the tree trunk. Dependent variable = the light intensity. Control variables = the same tree used for all measurements, the same light intensity meter, the same day/weather conditions.

7 September, 2015 Identifying variables and Designing Investigations Example No. 4 Listening to music impairs your ability to study. –T–T–T–Task 4: What are the independent, dependent and control variables in this experiment.

7 September, 2015 Identifying variables and Designing Investigations Example No. 4 Independent variable = whether the student is listening to music or not. Dependent variable = the students ability to recall information learned while listening to music (e.g. score on a memory test). Control variables = the same type of music, the same information to be learned.

7 September, 2015 Identifying variables and Designing Investigations Designing an experiment. Does a larger the surface area of a parachute, make the object fall slower? –T–T–T–Task 5: design an experiment to test this question Develop a hypothesis for this question Identify the variables (independent, dependent, control) – what are you going to change? How will you change it? What will you measure? How will you measure it? What needs to be kept the same to make the experiment a fair test?

7 September, 2015 Identifying variables and Designing Investigations Designing an experiment. What is the optimum temperature needed for the enzyme amylase to work? –T–T–T–Task 6: design an experiment to test this question * Develop a hypothesis for this question. * What are the independent and dependent variables? How will you make it a fair test? How many different temperatures will you test? How will you measure the results? * What type of graph would be most appropriate to communicate the results?