1 / 14

Data Analysis and Reporting

Data Analysis and Reporting. It’s an outliar !. Histogram. Similar to a bar graph but u ses data that is measured. . Stem-and-Leaf Displays. Show the distribution of a quantitative variable, like histograms do, while preserving the individual values. Stem-and-Leaf Display.

harmon
Download Presentation

Data Analysis and Reporting

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Data Analysis and Reporting It’s an outliar!

  2. Histogram • Similar to a bar graph but uses data that is measured.

  3. Stem-and-Leaf Displays • Show the distribution of a quantitative variable, like histograms do, while preserving the individual values.

  4. Stem-and-Leaf Display • 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.

  5. Dotplots • A dotplotis 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.

  6. Shape of Data • One single central peak or several separated peaks? • The peaks are called modes. • One peak isUnimodal. • Two peaks is called Bimodal. • More than two peaks is called Multimodal. • Straight across is called uniform.

  7. Shape of Data • If the histogram can be folded vertically in the middle and have the edges match pretty closely, the histogram is symmetric.

  8. Shape of Data • 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 Left Skewed Right

  9. Shape of Data • 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.

  10. Shape • 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

  11. Box and Whiskers • 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.

  12. Box and Whiskers • 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 25th and 75thpercentiles of the data, so… • The IQR contains the middle 50% of the values of the data.

  13. Box and Whiskers • 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.

  14. Box and Whiskers • 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, *.

More Related