1.What are the time Series graph explain with the help of example?

2.What is histogram ? How isit found when..
1.classinterval are equal.
2.classinterval are unequal.

3.Write notes on false base line ?

4.In what respect frequency curve is different from frequency polygons ?

5.Different between diagrammatic and graphical preparations ?

Dear Student

1)Time Series graph represents the changes in value of a variable over time or with the progress of time . As for example if we plot population changes of a region over a period of ten years it will be called a time series graph . First we need to take the successive years on the X-axis and the corresponding population figures on the Y-axis . Now we plot the line joining the ten points on the two dimensional plane and we obtain the time series graph .

2)A histogram can be defined as a diagram consisting of rectangles whose area is proportional to the frequency of a variable and whose width gives us the class interval . It is the most common form of diagrammatic representation of a grouped frequency distribution .
a) When class intervals are equal we simply plot class intervals on the horizontal axis and frequency on the vertical axis and draw the rectangles .
b) Now for unequal class interval we find out the frequency density . To find it we divide frequency by corresponding class width . Then we plot the class intervals on the horizontal axis and frequency density on the vertical and draw the rectangles .


  3) One of the things that we keep in mind while constructing graphs is that the scale on the Y-axis should begin from zero. Where the lowest value to be plotted on the Y scale is relatively high and a detailed scale is required to bring out he variations in all the data, starting the Y scale with zero introduces difficulties. For example, if we have a series of production figures over a number of years ranging from 15000 units to 25000 units, then starting with a zero origin would have one of two undesirable consequences: either (i) the necessarily large intervals (say 5000 units) on the Y scale would make us lose sight of the extent of fluctuations in the curve : (ii) a necessarily large graph to permit small intervals (say 1000 units) would cause a waste of a large part of the graph, in addition to poor visual representation . 

The solution is to break the Y scale : If the zero origin is the shown then the scale is broken by drawing a horizontal wavy line (also called kinked line) or a vertical wavy line between zero and the first unit on the Y scale which in our illustration would be 15000 units. These lines are drawn to make the reader aware of the fact that false base has been used. Three important objects of false base line are :

 Variations in the data are clearly shown

 A large part of the graph is not wasted or space is saved by using false base

 The graph provides a better visual representation

4) By joining the class mark against the frequency or by joining the mid points of the rectangles of a histogram we get the frequency polygon . Frequency curves and polygons are drawn in the same manner and the concept is same except that the curve is drawn using free hands and it is a smooth curve while polygon is drawn using a scale and it is line segments joint together .

5) Diagrammatic representation of data is dome using diagrams such as histogram , pie chart etc . While graphical representation deals with plotting of data on a two dimensional graph and representing the points with a line joining them .

Regards .



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