reading notes chapter 9 - Chapter 9(1-4 Most questions that we ask about large populations are translated into questions about specific summary

# reading notes chapter 9 - Chapter 9(1-4 Most questions that...

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Chapter 9 (1-4) - Most questions that we ask about large populations are translated into questions about specific summary characteristics of the group - Parameter: a number that is a summary characteristic of a population, a random situation, or a comparison of populations o “Population parameter” is a phrase used to make it clear that a parameter is associated with a population instead of a sample o Examples the proportion of adults in the world who are left-handed o Parameters have fixed, unchanging values o Usually, the value of a parameter is not known to us, and will not be known to us because we will not be able to measure every unit in the population o Although we will not have the information necessary to find the numerical value of a population parameter, we will be able to use statistical methods to make a good guess - Statistic/sample statistic: a number that is computed from a sample of values taken from a larger population o Summary characteristic of the sample data o The sample data may be collected in a sample survey, an observational survey, or an experiment - Sample estimate/estimate: a sample statistic when the statistic is used to estimate the unknown value of a population parameter - Possible values of sample statistics are variable - If two different samples are taken from the same population, it is likely that the sample statistics will be different for those two samples - The value of a sample statistic may change from sample to sample, and we will know the value once we have measured a sample - Statistical inference: when information from a sample is used to make generalizations about a larger population. Sample statistics are used to make conclusions about population parameters. Confidence intervals and hypothesis tests are two common statistical inference techniques - Confidence interval: an interval of values that the researcher is fairly sure will cover the true, unknown value of the population parameter o We use a confidence interval to estimate the value of a population parameter - Hypothesis testing/significance testing: uses sample data to attempt to reject a hypothesis about the population o Usually, researchers want to reject the notion that chance alone can explain the sample results o In most research settings, the desired conclusion is that the variables under scrutiny are related o Hypothesis testing is applied to population parameters by specifying a null value for the parameter – a value that would indicate that nothing of interest is happening
o Hypothesis testing proceeds by obtaining a sample, computing a sample statistic, and assessing how unlikely the sample statistic would be if the null parameter value were correct o In most cases, the researchers are trying to show that the null value is not correct o Achieving statistical significance is equivalent to rejecting the idea that the observed results are plausible if the null value is correct -

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