# STAT1250.docx - STAT1250 WEEK 1 u2013 WHAT IS STATISTICS...

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STAT1250 WEEK 1 – WHAT IS STATISTICS What is Statistics? Statistics is the science of learning from data, in other words , converting data to information. Statistics involves designing a study, then collecting, presenting, analysing data and interpreting the results. Objectives A primary objective of a statistician is to obtain information about a target population, using a sample. The target population comprises all relevant subjects of interest. The sample is a manageable subset, selected to make the study feasible. Scope of a Statistical Study Study Design Formulate the question of interest (What? Why? Who?) Specify the target population (Who/What? Where? When?) Determine how to select a sample Determine the measurements to be collected (the variables). Define the method of data collection (How? When? Where?) Populations and Samples The target population should be well defined The sample should be representative of the target population (not biased), and large enough to give accurate information about the population. Ideally, the observations should independent of each other. Selecting a sample
Only representative samples should be used to make reasoning about the target population A representative sample should be unbiased and large enough to be accurate To ensure the sample is a representative of the target population is to obtain a random sample A simple random sample is one in which each member of the target population has an equal chance of being chosen. Types of studies An observational study is one in which there is no intervention by the investigator nor is there any treatment imposed An experimental study is one in which the investigator has some control over the determinant The Data We Collect: Variables - Measurements are taken on subjects according to the variables of interest - Measurements vary from one subject to another - When collecting data we collect “values” of the variables - Values differ randomly between subjects, these variables are often called random variables