[Music] in the conductive quantitative research researcher need to answer the question how many respondents do we need in our study especially if the population is large enough doing a census will require a longer time and relatively higher cost therefore researchers select a sample from the population remember sample is a subset of the population hello everyone welcome I am teacher Sherwin in this video we are going to learn how to compute for sample size in our quantitative study before we can compute for our sample size we need to consider few things about our Target population and the sample that we need we need to determine our population size margin of error confidence level and degree of variability first the population size researchers need to determine how many people fit in the identified demographic for example if you want to know about the willingness of mothers to get vaccinated in a certain locality it is not practical to conduct a survey of all the mothers in the identified area therefore taking a sample is more appropriate than doing a census second margin of error in doing a quantitative research no sample will be entirely perfect as researchers we need to decide how much error to allow by definition the margin of error determines how much higher or lower than the population mean you are willing to let your sample mean fall often this is expressed in terms of percentage example plus minus five percent for example a researcher finds that 70 of the students selected the modular learning approach with a margin of error of plus minus five percent then the researcher can conclude that between 65 percent and 75 percent of the students in the population have selected modular learning approach third is the confidence level or the risk level this asks the question to the researchers how confident do you want to be that the actual mean fault within your confidence interval the most common confidence intervals are 90 percent 95 and 99 percent the key idea for confidence level tells the researcher that if the population is repeatedly sampled the average value of the attribute obtained by those samples is equal to the true population value fourth is the degree of variability or the standard deviation this asks the question how much variance do you expect in your response since we haven't actually administered a survey yet the safe decision is to use 0.5 it is often used in determining a more conservative sample size that is the sample size may be larger than if the true variability of the population attribute were used let us consider this example for population that is large enough Cochran 1963 develop this equation to compute for the sample size where N Sub Zero will be the computed sample size Z is the critical value of the desired confidence level e is the desired margin of error p is the estimated proportion of an attribute that is present in the population and cure will be computed by 1 minus p to illustrate suppose we wish to evaluate a Statewide Agricultural Extension program in which farmers were encouraged to adopt a new farming technology assume there is a large population but that we do not know the variability in the proportion that will adopt the new farming technology therefore assume P equal to 0.5 and suppose that we desire a 95 confidence level and plus minus five percent margin of error first we need to get the value of Z remember that Z is the critical value of the desired confidence level the value of Z at 95 confidence is 1.96 substitute the values in the given equation at 95 confidence level 5 margin of error and an assumed variability of 0.5 the required sample size is 385 or 385 farmers let us try this another formula of Imani 1967. where small letter N will be the computed sample size the capital letter N is the population size and E represents the margin of error this should be remembered clearly that this equation assumed a confidence level of 95 percent and a proportion of 0.50 again this equation assumed a confidence level of 95 percent and a proportion of 0.50 Suppose there are 2 000 farmers in certain locality you want to conduct a survey on their willingness to adopt the new farming technology the margin of error is five percent using the equation we need to have 333 Farmers to be respondents in our study in this video we learned how to compute for sample size [Music] thank you