Data handling

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1. Data Handling Data Handling is a part of statistics. Statistics is also a science of numbers. Statistics deals with the methods of collection, classification, analysis…
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  • 1. Data Handling Data Handling is a part of statistics. Statistics is also a science of numbers. Statistics deals with the methods of collection, classification, analysis and interpretation of such data. Any collection of information in the form of numerical figures giving the required information is called data.
  • 2. Two types of Data Depending on the type of data  Raw data  Grouped Data Depending on the method of collection  Primary Data  Secondary Data
  • 3. Definition of Variable As far as statistics is concerned the word variable means a measurable quantity which takes any numerical value within certain limits. Few etxamples are  (i) age,  (ii) income,  (iii) height and  (iv) weight.
  • 4. Definition of Frequency Suppose we measure the height of students in a school. It is possible that a particular value of height say 140 cm gets repeated. We then count the number of times the value occurs. This number is called the frequency of 140 cm. The number of times a particular value repeats itself is called its frequency.
  • 5. Definition of Range The difference between the highest value and the lowest value of a particular data is called the range.  Example - Let the heights (in cm) of 20 students in a class be as follows. 120, 122, 127, 112, 129, 118, 130, 132, 120, 115, 124, 128, 120, 134, 126, 110, 132, 121, 127, 118. Here the least value is 110 cm and the highest value is 134 cm.  Range = Highest value – Lowest value
  • 6. Class  In the above example if we take 5 classes say 110 - 115, 115 - 120, 120 – 125, 125 - 130, 130 - 135 then each class is known as class interval. The class interval must be of equal size. The number of classes is neither too big nor too small.  Optimum number of classes is between 5 and 10.  In class 110 - 115, 110 is called the lower limit of the class and 115 is the upper limit of the class.
  • 7. Class Interval There are two types of class intervals. They are  Inclusive form - The lower limit as well as upper limit will be included in that class interval. For example in first class interval 110 - 114, the heights 110 as well as 114 are included.  Exclusive form - the first class interval 110 - 115, 110 cm is included and 115 cm is excluded. In the second class interval 115 is included and 120 is excluded and so on. Since the two class intervals contain 115 cm, it is customary to include 115 cm in the class interval 115 – 120.
  • 8. Tally Marks  The height 110 cm, 112 cm belongs to the class interval 110 - 115. We enter | | tally marks. Count the tally marks and enter 2 as the frequency in the frequency column.  If five tally marks are to be made we mark four tally marks first and the fifth one is marked across, so that | | | | represents a cluster of five tally marks.  To represent seven, we use a cluster of five tally marks and then add two more tally marks as shown |||| ||.
  • 9. Frequency Table A table which represents the data in the form of three columns, first column showing the variable (Number) and the second column showing the values of the variable (Tally mark) and the third column showing their frequencies is called a frequency table
  • 10. Frequency Table If the values of the variable are given using different classes and the frequencies are marked against the respective classes, we get a frequency distribution.  Tabulation of Data - All the frequencies are added and the number is written as the total frequency for the entire intervals. This must match the total number of data given. This process of forming a frequency table is called tabulation of data.
  • 11. Frequency Table for Inclusive Data Class Interval Tally Mark Frequency 110 - 114 || 2 115 - 119 ||| 3 120 - 124 |||| | 6 125 - 129 |||| 5 130 - 134 |||| 4 Total 20
  • 12. Frequency Table for Exclusive Data Class Interval Tally Mark Frequency 110 - 115 || 2 115 - 120 ||| 3 120 - 125 |||| | 6 125 - 130 |||| 5 125 - 130 |||| 4 Total 20
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