10.Observation Unit.no.1

10.Observation
i) Variable and Constant:
1.     A measurable quantity which can vary from one individual to another is called a ‘variable’.  Examples are heights and weights of students in a class, prices of commodities, number of children in a family, etc.  It is denoted by the last letters of alphabets, i.e., x, y, and z.
2.     ‘Constant’ is a quantity which can assume only one value.  Examples are p = 3.14159, = 2.71828, etc.  It is usually denoted by the first letters of alphabets, i.e., a, b, c, d, …
ii) Continuous or Discrete Variables:
1.     A variable which can assume any value within a given range is called a continuous variable.  For example, the heights and weights of students, temperature, speed, etc.  the height of a student can be 62”, 62.5” or 62.45”.
2.     A variable which can assume only some specific values within a given range is called a discontinuous or discrete variable.  For example, the number of houses in a town, number of children in a family, number of students in a class, etc.  a discrete variable takes on values which are integers or whole numbers like 0,1,2,3,4,5, … but cannot be 2.5, 3.3, 3.91, 14.235, etc.  There cannot be 4.5 houses in a town or 10.15 number of students in a class, etc.
iii) Quantitative and Qualitative Data:
1.     Quantitative variables are heights, weights, temperature, speed, etc.
2.     Qualitative data are described by qualitative variables, such as marital status, religion, colour, race, etc.