23. Mean, Pictographs, Joint Bar Graph Pie Chart Statistics

 

23. Mean, Pictographs, Joint Bar Graph Pie Chart Statistics

Learn and Remember:

1) Raw data : The primary information collected for some special purpose is called raw data.

2) Observation : Every number in a statistical data is called an observation.

3) Frequency : Repeated occurrence of a particular number in the given data is called the frequency of that number.

[A] Mean : (i) The average of the observations of a statistical data is called the mean.

 Mean = ^{Sum of observations} ⁄ _{Number of observations}

If X1 + X2 + ... +Xn  be n given observations, then their mean = X1, X2, ..., Xn ⁄ n

(ii) Mean of ungrouped data :

If X1, X2, ..., Xn be the observations with frequencies .

F1,F2, ....Fn  respectively, then X1 is repeated F1 times, X2 is repeated F2 times, etc

∴ on addition of observations we write F1X1,F2X2,........Fn Xn.

 Mean of the given data = ^{F1X1,F2X2..... ..Fn Xn} ⁄ _{F1 , F2 ,......Fn} = ¹ ⁄ _{n  ∑Fi Xi.}

∑' is the symbol for summation. n=∑fi= total number of observations.

[B] Joint Bar Graphs : Bar graphs showing different information and joined together are called joint bar graphs.

(1) The distance between consecutive joint bar graphs should be the same.

(2) Joint bar graphs are useful to compare two or more quantities of the same type.

[C] Pie Diagram : In a pie diagram, the values of items or components are represented by sectors of a circle formed by using a convenient radius.

Central angle (θ)=  Value of the item or component ⁄ Total value of all the items of components  × 360°

 Reading the pie diagram : The data already represented in a pie diagram can retrieved when needed. Comparison of items from two pie diagrams can be done