Variables, fair tests, anomalies, accuracy and precision, random and systematic errors, and the words scientists use about investigations.
What you will learn
- Name the independent, dependent and control variables
- Spot an anomaly and work out a mean without it
- Tell accurate from precise
- Tell random from systematic errors
- Give the resolution of an instrument
Three kinds of variable
The independent variable is the one you change on purpose.
The dependent variable is the one you measure to see the effect. Control variables are kept the same, so that only the independent variable can cause a change.
Then the test is valid: it answers the question it set out to. A variable is continuous if it can take any value (sugar concentration, temperature) and categoric if it comes in named groups (type of sugar).
A hypothesis is a prediction that an investigation can test, such as "the higher the temperature, the faster yeast respires".
- investigation: does temperature change how fast amylase breaks down starch?
- independent: the temperature
- dependent: the time until iodine no longer turns blue-black
- control: the volume of amylase, the starch concentration, the pH
The rest of this lesson and its 10 practice questions are locked.
In this lesson
- Three kinds of variable
- Repeats, anomalies and means
- Accurate, precise and errors
- Try it: An easy one first
10 practice questions, marked as you go; about 20 minutes in all.
Key terms
Independent variable, Dependent variable, Control variables, Continuous, Categoric, Hypothesis, Repeatable, Reproducible, Accurate, Precise
In this unit: Required practicals and maths skills
The skills behind every biology practical: units and magnification, means and percentages, rates and graphs, sampling, ratios and planning.