1 Introduction Statistics 1.1 Meaning of Statistics “Number of car accidents has been decreased 10 percent from last year.” “There are 500 newly reported COVID-19 cases in 5 days.” The previous examples are results from collecting and analysing data. What is data? Data means statements or numbers from observing, counting, measuring or asking. Statistics is the study of methods for collecting, analyzing, interpreting, presenting data. Why study statistics? • Understanding • Prediction • Making Decision We know that “Number of car accidents has been decreased 10 percent from last year,” because of the government policy to reduce the speed limit. Then we can predict that the number of car accident will be reduced if the government has a similar policy. So, the government can make a plan to reduce a number of car acident for next year. We know “there are 500 new newly reported COVID-19 cases in 5 days” because of many people were travelling during this time. So, a number will increase if the government still allows the travelling. Therefore, the government will have to enforce some restriction for this. 1.2 Data Sets There are two types of data sets. 1. Population is all objects or people that we are interested. 2. Sample is a part of population. Why we need sample? • Size of population is huge. It is difficult to gather data from the entire population. • Use sample as a representation of population. 1.2.1 Example. Population VS Sample 1. A researcher would like to know how many Chiang Mai people are lactose intolerant. So, 1000 Chiang Mai people were asked if they are lactose intolerant. Population is .......................................................................... Sample is .......................................................................... 2. During the president election of United States in 2020, a researcher would like to predict who is going to be the next president. So, there are 10,000 people from American citizen who are able to vote a president. wereasked Population is .............................................................................. Sample is .......................................................................... 1.3 Types of Data 1. Qualitative: Color, Gender, Satisfactory, etc. 2. Quantitative: Age, Height, Weight, etc. 1.4 Data Collection 1. Experiment 2. Simulation 3. Census 4. Sampling Exercises 1. What is the meaning of ”population”? 2. What is the meaning of ”sample” 3. A researcher wants to study political attitudes in young people in Chaing Mai province. The researcher survey 300 students in many schools in Chiang Mai province. What are the population and sample for this study. 4. Give examples of data which are quantitative. 5. Give examples of data which are qualitative.
