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# Statistics

#### Math Review of Scatterplots, Trend Lines, and Median-Fit Lines

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Overview Data in real-world situations doesn’t always fall into neat linear relationships. The actual values may be plotted in a scatterplot. Trend lines approximate the direction and size of the relationship between data points, as do median-fit lines. Scatterplots Actual data values can be plotted by ordered pairs on a graph called a scatterplot. The…

#### Math Review of Descriptive Statistics

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Overview Descriptive statistics are measurements of a data set that summarize information about the raw scores. Some types include distributions of scores, measures of central tendency, and measures of variability. Distributions of Scores Data can be organized into frequency distributions of various types.  Suppose 100 students were given a 20-item rating scale called the Test…

#### Math Review of Relative Frequency

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Overview: Relative frequencies refer to estimates of probabilities taken from actual data.  Suppose that a survey of 1000 voters is taken and 213 of them state that they are going to vote in favor of a certain issue.  The relative frequency would be 213/1000 or .213. Difference between Probability and Relative Frequency Suppose that a…

#### Math Review of Fitting a Line to Data

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Overview: When data points are plotted onto a standard graph, that is only the first step in determining the nature of the relationship.  The next step is to determine if the data follow a linear relationship, and then fit a line to the data.  While a line might not describe all the data points, if…

#### Representing Data: Ranges, Quartiles, and Box-and-Whisker Plots

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Overview: Raw data from any series of measurements, such as test scores, heights, or sales figures, usually needs to be organized in some way before it can be used.  One of the ways that data can be organized is in a frequency distribution.  Then the range of data can be determined and other measurements of…

#### A Statistics Review of Confidence Intervals

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Overview:  What Is a Confidence Interval? Unless the population is small enough to determine each member, researchers cannot know the exact value of the population mean.  However, using statistical techniques, it can be predicted that the mean falls within a certain range, called the confidence interval.  Using properties of sample size, standard deviation, and probability…

#### Who’s Afraid of the Normal Curve?

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Overview:  What Is the Normal Curve? The normal curve is a frequency distribution with special statistical properties.  The best-known application of the normal curve is the distribution of intelligence as measured by tests such as the Stanford-Binet, but there are other examples  that are close to the normal curve in human and animal behavior.  Biologists,…

#### Statistics: How to Use Frequency Distributions

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Overview:  What Is A Frequency Distribution? A frequency distribution can yield a lot of information about the results of an experiment or survey, even before any more complex statistical analysis is done.  In its simplest form, a frequency distribution is just an organized tally of how many times an event occurs.  It can be stated…

#### Keeping Statistics Honest: How Not to Lie with Statistics

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Overview:  Statistics Are Not Lies The use of statistics has really gotten a bad name.  No less a personage than Mark Twain once said something about lies and statistics, and every day some advertiser makes a claim that uses numbers but cannot be verified, or someone reporting the news uses a statistic that makes listeners… ### 1-877-545-7737  