Category Archives: Statistics

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

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

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

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

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 […]

A Statistics Review of Confidence Intervals

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 […]