GCSE Chemistry Key Words

Prcise measurement are ones in which ther is verry little spread about the mean value.

Precision depends only on the extent of random errors-It gives no indication on how close results are to the true value.

A reliable measurement is one that consistently remains the same after several repeats.

A measurement is repeatable if the origional experimenter repeats the investigation using the same method and equipment and obtains the same results

A measurement is reaproducible if the investigation is repeated by another person or by using different equipment or techniques, and the same results are obtained.

Theese are physical, chemical or biological quantities or charactaristics.

Continuous variables can have values (called a quantity) that can be given a magnitude either by counting (as in the case of the number of shrimp) or by measurement (eg light intensity, flow rate ect) 

Categoric variables have values that are labels. Eg names of plants or types of material.

A control variable is one wich may in addition to the independant variable, affect the outcome of the investigation and therefore has to be kept constant or at least monitored.  

The dependant variable is the variable of which the value is measured for each and every change in the independant variable. 

The independant variable is the variable for which values are changed or selected by the investigator

A proposal intended to explain certain facts or observations