Quantative: variables, scales of measurement, validity & reliability

Quantative: variables, scales of measurement, validity & reliability

1. variables

   • factors that you are interested in within a research study
   • independant variables
     • assumed to remain constant or uninfluenced by changing conditions or circumstances in the study
     • IV
     • treatment in the study
     • values of IV are called levels
   • dependant variables
     • changes in ways that are determined by the influence of an independant variable or external factor
     • DV
     • response outcome measures

2. measurement

   • catagorical measurement
     • variables with discrete value
       • incremental placement, is or isnt a characteristic, binary scales, ordinal = nominal scale
     • assign values and variables
     • measured nominal or ordinal scales
   • process of description and quantification
   • recording of physical or behavioural characteristics by assigning value to the quality, quantity, frequency or degree of these attributes
   • also using a tool to measure
   • assign value to an object
     • directly- length, width, death rate
     • indirectly - temp.
   • continuous measurement
     • measured along an infinetly desirable scale
     • continuous variables - height, weight
     • can be measured using interval or ratio scales
     • continuous data can be transformed into catagorical data, but not vise versa

3. NOIR- nominal, ordinal, interval, ratio

4. NOMINAL SCALES MEASUREMENT

   • classifying observation into mutually exclusive groups, male/female

5. ORDINAL SCALES OF MEASUREMENT

   • ranking catagorical data
   • shows relative magnitude not quantity, i.e. strongly disagree- strongly agree
   • relative ranking of the levels of the attribute

6. interal scales

   • equal spacing between catagories
   • indicates how much the catagories differ
   • demonstrates equal amount of change in a variable between equivalent distances or intervals
   • data scale does not have a true 0
   • cannot make statements made concerning ratios

7. ratio scales

   • represent highest level of measurement
   • absolute 0
   • can describe ratio properties between values

8. reliability & validity

   • measurement error or measurement bias
   • reliability
   • validity
     • internal validity
       • is the degree to which observations taken during the study may be attributed solely to the hypothesised effect being studied
     • external validity
       • the extent to which the finding of the study can be generalised to the population