 Hello and welcome to the session. In this session we will discuss about statistics. Basically, statistics is the area of study dealing with the presentation, analysis, interpretation of data. Now let's see what is data? Facts or figures collected with a definite purpose are called data. Every part of our lives utilizes data in one form or the other. So it becomes essential for us to know how to extract meaningful information from such data. This extraction of meaningful information is studied in a branch of mathematics which is called statistics. Now we discuss about collection of data. Now when the information is collected by the investigator herself or himself with a definite objective in her or his mind, the data obtained is called primary data. And when the information gathered from a source which already had the information stored, the data obtained is called secondary data. Such data which has been collected by someone else in another context needs to be used with great care ensuring the source is reliable. Now we discuss presentation of data. As soon as the work related to the collection of data is over, the investigator has to find out the ways to present them in a form which is meaningful, easily understood and gives its main features at a glance. Data obtained in original form is called raw data or the ungrouped data like data given in this form is called raw data. Then the difference of the highest and the lowest values in the data is called the range of the data. Like in this case you can see that this is the highest value and this is the lowest value. Now the difference is the range of the data. Consider this data which gives the number of children in 20 families. As you can see that the number of observations in this experiment is large. So for this we will make an ungrouped frequency distribution table or a frequency distribution table. This is the ungrouped frequency distribution table or we can also say a frequency distribution table. From this data you observe that the number of families which have one child is five, number of families which have two children is six, number of families which have three children is four, number of families which have four children is three and number of families which have five children is two. We can also use tally marks to represent this data. This is how we represent the data using the tally marks. This data gives marks out of 50 obtained by 30 students of a class in a test to present such a large amount of data so that a reader can make sense of it easily. We condense it into groups and we call these groups classes or class intervals. So observing this data we can form the class intervals as 0 to 10, 10 to 20, 20 to 30, 30 to 40 and 40 to 50. Now from this data we observe that the number of students who obtain marks in the range of 0 to 10 is 6. Then number of students who obtain the marks from 10 to 20, 11, then 20 to 30 would be 5, 30 to 40 would be 4 and 40 to 50 would be 4. Now in the interval 0 to 10 we include 0 but we exclude 10. That is here the number of students that is 6 are those students who have obtained the marks from 0 to 9. The student who got 10 marks will not be included in this class interval. So these are the class intervals. Now their size would be the class size or the class width. That is in this case the class size or the class width would be equal to 10. That is the size of each class interval. And in each of these classes the least number is the lower class limit and the greatest number is the upper class limit. Like if you consider the class interval 0 to 10 in this 0 is the lower class limit and 10 is the upper class limit. Presenting the data in this form which simplifies and condenses data and enables us to observe certain information at a glance is called grouped frequency distribution table. So this is how we can represent the data in grouped frequency distribution table. This completes the session. Hope you have understood the concept of collection of data and presentation of data.