MATHEMATICS FOR ENGINEERING STATISTICS （工程数学统计）.pdfVIP

MATHEMATICS FOR ENGINEERING STATISTICS TUTORIAL 1 – BASICS OF STATISTICAL DATA This tutorial is useful to anyone studying engineering. It uses the principle of learning by example. On completion of this tutorial you should be able to do the following.  Explain the use of raw data.  Present data as frequency polygons, bar graphs and histograms.  Explain and find the mean and median values.  Explain and plot ogives.  Explain and find quartiles.  Explain and find the standard deviation and variance for grouped and ungrouped data. © D.J.DUNN 1 1. INTRODUCTION Statistics are used to help us analyse and understand the performance and trends in various areas of work. These might be financial trends, things to do with the population or things to do with manufacturing. Often we wish to present information visually with easily understood graphics and so a variety of graphs and charts are used for this purpose. Here is an example of a PIE CHART and a BAR CHART showing the number of parliamentary seats won by main political parties at the 2001 British general election. The number of MPs elected must be a round or whole number so the raw data is exact. When presenting other forms of data this is not the case as explained in the following section. 2. RAW DATA Let’s use an example to get started. Consider a set of statistics compiled for the height of children of age 10. First we would compile a table of heights. This would be the raw data. Note that the larger the sample we take, the more meaningful the results will be. Suppose we measure the heights to an accuracy of 0.01 m. This is the table of raw data for 10 year old children Sample 1 2 3 4 5 6 7 8 9 10 11 12 Height (m) 1.45 1.56 1.37 1.44 1.