Statistics
Statistics : The methods of analysis of any collection of data are covered by the branch of mathematics called Statistics.It is the study of the collection, organization, analysis, and interpretation of data.It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments.
Measures of central tendency is also included in statistics. The mean, median and mode are the measure of Central Tendency.
It is difficult to draw conclusions from a large amount of numerical data. So if data are represented pictorially, then it is very easy to understand. The data can be represented by many ways, such as Bar graph, Histogram, Pie chart etc.
The advantages and disadvantages of some graphs are as follows:
Pictograph: It is way of of representing data using pictures or small images.  Advantages Reading a pictograph helps in interpreting the pictograph so as to get the information from it. 
Disadvantages For each and every data drawing of images or pictures is not possible.Example : Population of different cities 

Bar graph : When numerical data is presented as columns on a graph this graphical representation of data is called Bar graph or Column graph.  Advantages We can easily compare two or three sets of data. 
Disadvantages Sometimes numerical values of items may be so large that it may not be possible to represent them by exact lengths of a column. 

Histogram : A histogram is pictorial representation of the grouped data in the form of rectangles. There is no gap in each rectangles.Each base of the rectangles represent the class interval and whose heights correspond to frequencies. 
Advantages We represent frequency distribution of the grouped data. 
Disadvantages As this is drawn using class interval so class limits need to be real. So true class limits can be found out using continuous grouped frequency data. 

Pie chart : It is a simple way of presenting a simple data in a circle as a sector form.  Advantages 1) As the data represented are in the form of sectors we need to find the degrees of each data. 2) We can easily compare the data using the size of the sector. 3) We can compare each sector with the total amount easily. 
Disadvantages A pie chart should not be used if there are too many items to played as it will look clustered and confusing. 
Another way of representing data is tabular form in order to study their salient features. Such as arrangement is called presentation of data.
The raw data when put in ascending or descending order of magnitude is called an array.
There are different way in which data can be represented.
The raw data can be arranged in any one of the following ways :
1) Serial order of alphabetical order.
2) Ascending order.
3) Descending order.
Statistics
• Statistics
• Pictograph
• Pie chart
• Bar Graph
• Double Bar Graph
• Histogram
• Frequency polygon
• Frequency distribution (Discrete )
• Frequency distribution( continuous or grouped)
• Measures of central tendency ( Mean, Mode and Median)
• Ogive or Frequency curve.
7th grade math
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