 Hello and welcome to this session. In this session we will recognize the purposes of and differences among sample surveys, experiments and observational studies and we will explain how random observations relates to each. And now we will discuss three methods of data collection. First is sample survey, second is experiment and third is observational study. Wherever we want to draw a conclusion for a population, we use a sample from the population and investigate it according to our need. But sometimes sample is not an appropriate method of data collection and we have to use experiment or observational study to draw the conclusion. Now let us discuss all one by one and let us discuss sample survey. Now a sample survey is a study that obtains data of a population called sample, the results for population. For example you want a sample collection for the captain in your school, not go to each student and ask their opinion, rather you will collect a sample of students depending on size of population. The conclusion about the opinion of all the students in your school is the best method to know the result survey. Now the sample collected should be selected according to should be a true representative of the population. It should be selected randomly, it means the population being selected. The sample collected should be the size of population and it should be selected randomly. Now let us discuss the study. Now suppose a company wants to know does its smart tutorial software will improve the algebra skills of high school study. Now for this we create all students, rather the company will follow an experimental study to know its effect. The company will randomly choose students may be 120 students who were not using the software. Now the company will randomly select out of these 120 students and give them the software to use, a given software to use as 60 students are left as it is. Now after 6 months the algebra skills software will be compared to the algebra skills who did not use the software. In the two groups the company will draw a conclusion about its software. Now where will best the software on 60 students in order to observe their response? There is the group on which we impose the software is called, hence was typically compared to the 60 students who did not use software. So that group is called confirm group experiments deliberately impose some treatment on individuals in order to observe their response. This is probably compared to that of a control group is a group of individuals who are given no treatment. The individuals at random treatment that control group this randomization will produce groups of individuals that are theoretically similar in all ways before the treatment is applied. Now let us discuss observational study. Now in observational study are observed and no attempt is made to influence them. The researcher simply observes what the individuals do naturally. Suppose you want to find out what are the 10 years of smoking affect the lung capacity they will do. Observational study because we cannot impose smoking observe the lung capacity we are smoking for 10 years to the equal number of man smokers. The sample chosen is the smokers and smokers should be the random samples can be selected for the groups being studied and surveys do not compare groups and so do not address and affect observational studies and experiments are designed to be comparative that is to compare data from two or more groups looking for a relationship between variables that only a well-designed experiment can determine an effect relationship. So in this session we have discussed three methods of data collection that are simple survey experiment and observational study and this completes our session hope you all have enjoyed the session.