It’s an outliar!

 Similar to a bar graph but uses data that is measured.

 Show the distribution of a quantitative variable, like histograms do, while preserving the individual values.

 How to Construct:  First, cut each data value into leading digits (“stems”) and trailing digits (“leaves”).  Use only one digit for each leaf.  Either round or truncate the data values to one decimal place after the stem.

 A dotplot is a simple display. It just places a dot along an axis for each case in the data.  You might see a dotplot displayed horizontally or vertically.

 One single central peak or several separated peaks?  The peaks are called modes.  One peak is Unimodal.  Two peaks is called Bimodal.  More than two peaks is called Multimodal.  Straight across is called uniform.

 If the histogram can be folded vertically in the middle and have the edges match pretty closely, the histogram is symmetric.

 The (usually) thinner ends of a distribution are called the tails. If one tail stretches out farther than the other, the histogram is said to be skewed to the side of the longer tail.  The skew is the direction of the tail.  Skewed LeftSkewed Right

 You should always mention any stragglers, or outliers, that stand off away from the body of the distribution.  Are there any gaps in the distribution? If so, we might have data from more than one group.

 Always report a measure of spread along with a measure of center when describing a distribution numerically.  The range of the data is the difference between the maximum and minimum values: Range = max – min

 The median is the value with exactly half the data values below it and half above it. ◦ The median divides the data into two equal areas. ◦ Use the median as a measure of center when data is skewed.  We find the mean by adding up all of the data values and dividing by n, the number of data values we have. ◦ Use the mean as a measure of center when the data is symmetric.

 The interquartile range (IQR) lets us ignore extreme data values and concentrate on the middle of the data.  The lower and upper quartiles are the 25 th and 75 th percentiles of the data, so…  The IQR contains the middle 50% of the values of the data.

 The five-number summary of a distribution reports its median, quartiles, and extremes (maximum and minimum).  Box and Whiskers is a graphical display of the 5- number summary, and sometimes outliers, on a number line.

 Follow the following steps to test for outliers:  Step 1: Multiply the IQR by 1.5  Step 2: Add this value above to Q3  Step 3: Subtract the value in step 1 from Q1  Anything above the value in Step 2 is an outlier  Anything below the value in Step 3 is an outlier.  Display outliers as asterisks, *.