Mr C.S. Wood BSc MSc

Mr Wood has worked as a Grammar school head of department and science teacher for over twenty years and is an experienced GCSE examiner. He is an ex fish farm manager and disease inspector for the Ministry of Agriculture. This wealth of experience allows him to explain things in a real world context, to show you how to answer questions more effectively and where to pick up those extra hidden marks.

Control group

In controlled experiments, changes to the independent variable are applied to a treatment group. A control group will contain experimental subjects which receive no changes to the independent variable. This allows any uncontrolled variables that could mask the effects of a change in the independent group to affect both the experimental group and the control …

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Zero error

Any indication that a measuring system gives a false reading when the true value of a measured quantity is zero eg the reading on an mass balance failing to return to zero when nothing is being weighed.  A zero error may result in a systematic error. 

Validity

Suitability of the investigative procedure to answer the question being asked. For example, an investigation to find out if the rate of a chemical reaction depended upon the concentration of one of the reactants would not be a valid procedure if the temperature of the reactants was not controlled. 

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AQA GCSE Biology 4.1.1.(1-2) Cytology

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