need assistance and help to better understand the measurements and levels of measurement  in quantitative psychology

Properties of a Quantity

( Discrete Quantities ,Continuous Quantities)

levels of measurements  of psychological variables (Nominal, Ordinal, Interval and Ratio Scales)

it would be helpful if i could get examples and how they compare to each other and teach me when to use what 

also drawbacks of quantitative measurements in psychology  (eg: There Is No 'Best' Model Or Measurement Technique, Non-conscious measurement is limit)