3. VariablesIn any experiment there are 3 variables: An independent (changed) variable A dependent (measured) variable Some control variablesLet’s look at each type…
4. Independent Variable This is the thing you decide to changeeg. Investigating how plants grow when they are given different amounts of water You change the amount of water you give the plant. So, amount of water is the independent variable.
5. Dependent Variable This is the thing that changes as a result. This is the thing you measureeg. Investigating how plants grow when they are given different amounts of water You measure how much the plant grows. So, amount of growth is the dependent variable.
6. Control Variables These are all the things that must not change to make it a fair test. They must be kept the same. You need to keep the plants in the same place so that they get the same amount of sunlight or shade. You need to grow the plants in the same type of pot, that are the same size. The plants need to have the same type and same amount of potting mix. These are the control variables.
7. Summary The independent variable is changed. Amount of water The dependent variable is measured. Growth of plant. The control variables are kept the same. Amount of sunlight or shade. Type of pot. Size of pot. Type of potting mix, etc.
9. Change one thing, Measure one thing (usually),Keep everything else the same.
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11. Accuracy, Reliability and Validity
12. Accuracy The exactness or precision of a measurement; relating to the degree of precision in measurement. Highly dependant on equipment choice to measure values accurately
13. Reliability • The degree with which repeated observation and/or measurements taken under identical circumstances will give the same results.
14. Validity The extent to which the processes and resultant data measure what was intended. Are the measurements you recorded caused by the variables you think.
15. Reliability Have I tested with repetition? Have I chosen equipment that will giveAccuracy me accurate and precise readings? Does my experiment actually test the hypothesis that I want it to? WhatValidity variables have I identified and controlled?