MAT243 - 2.1 Survey sampling.doc - 2.1 Survey sampling Descriptive and inferential statistics Two types of statistical analysis exist to describe survey

# MAT243 - 2.1 Survey sampling.doc - 2.1 Survey sampling...

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2.1 Survey sampling Descriptive and inferential statistics Two types of statistical analysis exist to describe survey data: descriptive statistics and inferential statistics . Descriptive statistics focuses on summarizing survey data about a sample drawn from a population. Summary statistics include measures of central tendency such as mean, median, and mode; and dispersion such as range and standard deviation. Descriptive statistics cannot make conclusions based on the data. Rather, descriptive statistics is a way to present data in a meaningful way. Inferential statistics focuses on using information from the sample to make conclusions about the population from which the sample was drawn. The two primary methods of inferential statistics are confidence intervals, which specify the range within which a parameter falls with a given probability, and hypothesis testing, which allows differences between population parameters to be compared. Surveys Surveys are conducted to allow statisticians to make generalizations about a population. A population is any collection of objects, people, or things about which statistical inference are made. A parameter of a population is a numerical characteristic of a population, such as mean, median, or standard deviation. A sampling unit is an individual in the population on which a measurement can be taken. The sampling frame is the subset of the population from which a sample is drawn. The sample is composed of the sampling units that provide data to be collected. A statistic is a numerical characteristic of a sample, rather than the population. The following animation shows the relationship between the population, sampling unit, sampling frame, and sample. PARTICIPATION ACTIVITY

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2.1.1: Sampling a population. 1234 2x speed Population Sampling unit Sampling frame Sample The sample is the subset of the sampling frame from which measurements are actually taken. Feedback? The following animation shows the relationship between a parameter and a statistic. PARTICIPATION ACTIVITY 2.1.2: Parameters and statistics. 1234 2x speed Population Age 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 Sample A Sample B Joey Sally Population mean: 3 Parameter Sample A's mean: 2.8 Sample B's mean: 3.2 Statistics The population mean is a parameter. The mean of each sample is a statistic. Feedback?
Example 2.1.1: The Liraglutide Effect and Action in Diabetes: Evaluation of Cardiovascular Outcome Results (LEADER) clinical trial. The LEADER clinical trial was initiated in 2010 at 410 hospitals in 32 countries to evaluate the effect of liraglutide, a drug for treatment of type 2 diabetes, on the frequency of cardiovascular diseases such as heart attack, stroke, and heart failure ( Source ). The populations under study were type 2 diabetes patients with excessively high blood sugar taking either liraglutide or a placebo (an inactive drug). The parameters measured include blood sugar level, kidney function measurement, frequency of adverse effects and complications, and mortality rate. The overall goal of the trial was to determine

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