var presentation = ["<phrase>Key Terms for Intro Statistics<\/phrase>","<word>study a population<\/word>","<word>population<\/word>","<word>select a sample<\/word>","<word>sampling<\/word>","<phrase>In statistics, we generally want to <strong data-readahead=\"study a population\">study a population<\/strong>. You can think of a <strong data-readahead=\"population\">population<\/strong> as a collection of persons, things, or\nobjects under study. To study the <strong data-readahead=\"population\">population<\/strong>, we <strong data-readahead=\"select a sample\">select a sample<\/strong>. The idea of <strong data-readahead=\"sampling\">sampling<\/strong> is to select a portion (or subset)\nof the larger <strong data-readahead=\"population\">population<\/strong> and study that portion (the sample) to gain information about the <strong data-readahead=\"population\">population<\/strong>. Data are the result of\n<strong data-readahead=\"sampling\">sampling<\/strong> from a <strong data-readahead=\"population\">population<\/strong>.<\/phrase>","<word>practical technique<\/word>","<word>presidential elections<\/word>","<word>opinion poll samples of 1,000-2,000 people<\/word>","<word>represent<\/word>","<word>entire country<\/word>","<phrase>Because it takes a lot of time and money to examine an entire <strong data-readahead=\"population\">population<\/strong>, <strong data-readahead=\"sampling\">sampling<\/strong> is a very <strong data-readahead=\"practical technique\">practical technique<\/strong>. If you\nwished to compute the overall grade point average at your school, it would make sense to <strong data-readahead=\"select a sample\">select a sample<\/strong> of students who\nattend the school. The data collected from the sample would be the students' grade point averages. In <strong data-readahead=\"presidential elections\">presidential elections<\/strong>,\n<strong data-readahead=\"opinion poll samples of 1,000-2,000 people\">opinion poll samples of 1,000-2,000 people<\/strong> are taken. The opinion poll is supposed to <strong data-readahead=\"represent\">represent<\/strong> the views of the people\nin the <strong data-readahead=\"entire country\">entire country<\/strong>. Manufacturers of canned carbonated drinks take samples to determine if a 16 ounce can contains 16\nounces of carbonated drink.<\/phrase>","<word>calculate a statistic<\/word>","<word>statistic<\/word>","<word>represents a property of the sample<\/word>","<word>parameter is a number that is a property of the population<\/word>","<phrase>From the sample data, we can <strong data-readahead=\"calculate a statistic\">calculate a statistic<\/strong>. A <strong data-readahead=\"statistic\">statistic<\/strong> is a number that <strong data-readahead=\"represents a property of the sample\">represents a property of the sample<\/strong>. For\nexample, if we consider one math class to be a sample of the <strong data-readahead=\"population\">population<\/strong> of all math classes, then the average number of\npoints earned by students in that one math class at the end of the term is an example of a <strong data-readahead=\"statistic\">statistic<\/strong>. The <strong data-readahead=\"statistic\">statistic<\/strong> is an estimate\nof a <strong data-readahead=\"population\">population<\/strong> parameter. A <strong data-readahead=\"parameter is a number that is a property of the population\">parameter is a number that is a property of the population<\/strong>. Since we considered all math\nclasses to be the <strong data-readahead=\"population\">population<\/strong>, then the average number of points earned per student over all the math classes is an example\nof a parameter.<\/phrase>","<word>One of the main concerns<\/word>","<word>accuracy<\/word>","<word>inferential statistics<\/word>","<word>test the validity<\/word>","<phrase><strong data-readahead=\"One of the main concerns\">One of the main concerns<\/strong> in the field of statistics is how accurately a <strong data-readahead=\"statistic\">statistic<\/strong> estimates a parameter. The <strong data-readahead=\"accuracy\">accuracy<\/strong> really\ndepends on how well the sample represents the <strong data-readahead=\"population\">population<\/strong>. The sample must contain the characteristics of the <strong data-readahead=\"population\">population<\/strong>\nin order to be a representative sample. We are interested in both the sample <strong data-readahead=\"statistic\">statistic<\/strong> and the <strong data-readahead=\"population\">population<\/strong> parameter in\n<strong data-readahead=\"inferential statistics\">inferential statistics<\/strong>. In a later chapter, we will use the sample <strong data-readahead=\"statistic\">statistic<\/strong> to <strong data-readahead=\"test the validity\">test the validity<\/strong> of the established <strong data-readahead=\"population\">population<\/strong>\nparameter.<\/phrase>","<word>variable<\/word>","<word>characteristic of interest for each person or thing in a population<\/word>","<word>numerical or categorical<\/word>","<phrase>A <strong data-readahead=\"variable\">variable<\/strong>, notated by capital letters such as X and Y, is a <strong data-readahead=\"characteristic of interest for each person or thing in a population\">characteristic of interest for each person or thing in a population<\/strong>.\nVariables may be <strong data-readahead=\"numerical or categorical\">numerical or categorical<\/strong>. Numerical <strong data-readahead=\"variable\">variable<\/strong> stake on values with equal units such as weight in pounds and time in hours.\nCategorical variables place the person or thing into a category. If we let X equal the number of points earned by one math student at the end of a term, then X is a numerical <strong data-readahead=\"variable\">variable<\/strong>.<\/phrase>","<phrase>If we let Y be a person's party affiliation, then some examples of Y include Republican, Democrat, and Independent. Y\nis a categorical <strong data-readahead=\"variable\">variable<\/strong>. We could do some math with values of X (calculate the average number of points earned, for example), but it makes no sense to do math with values of Y (calculating an average party affiliation makes no sense).<\/phrase>","<word>Data are the actual values<\/word>","<phrase><strong data-readahead=\"Data are the actual values\">Data are the actual values<\/strong> of the <strong data-readahead=\"variable\">variable<\/strong>. They may be numbers or they may be words. Datum is a single value.<\/phrase>","<word>mean and proportion<\/word>","<phrase>Two words that come up often in statistics are <strong data-readahead=\"mean and proportion\">mean and proportion<\/strong>. If you were to take three exams in your math classes\nand obtain scores of 86, 75, and 92, you would calculate your mean score by adding the three exam scores and dividing by\nthree (your mean score would be 84.3 to one decimal place). If, in your math class, there are 40 students and 22 are men\nand 18 are women, then the proportion of men students is 22\/40 and the proportion of women students is 18\/40.<\/phrase>","<phrase>Download for free at\nhttp:\/\/cnx.org\/content\/col11562\/latest\/<\/phrase>"];
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