Work with Students Sitting Around You to Create Answers to These Questions

ACTIVITY SET 3

Work with students sitting around you to create answers to these questions.

Activity 3.1 In the Datasets folder of the website, click on the link for the dataset Class Survey (Minitab File). Data are from n = 226 students who completed the survey. In column C20 Book Cost are the responses to how much students expected to pay for books this semester.

a. Use Graph>Histogram click on Simple, and then enter Book Cost Variables box. to draw a histogram. Use the mouse to identify in the graph the characteristics of the various bars in the histogram. Do this to complete the following sentences.

The most frequently reported amount spent was between ___ and ___. Of the 226 students, ___ students said they spent that much.

The second most frequently reported amount spent was between ____ and ____.

b. Using Minitab, draw a boxplot of the Book Cost (Use Graph>Boxplot, select “Simple” and then enter Book Cost in the variable window). The boxplot provides a graph of the 5-number summary for a set of data.. By placing the mouse pointer over the “box” a pop-up will appear displaying part of the 5-number summary.

·  What do the * represent in a boxplot?

·  How many * are there for the variable Book Cost?

·  What are the outlier values? [place your mouse over the * to see the value]

·  What is the 5-number summary for Book Cost?

·  The shape of the data represented by the box plot can be determined by the location of the median bar in the box and by comparing the length of the “whiskers” – the two lines that extend from either end of the box. If the median is in the center and the whiskers are of roughly equal length then the data is symmetrical. If the median is near the bottom of the box and the top whisker is longer, then the distribution is said to be skewed to the right or positively skewed. If the median is near the top of the box and the bottom whisker is longer, then skewed to the left or negatively skewed. What is the shape of Book Cost based on the boxplot? Does this concur with how you would interpret the histogram?

·  The whiskers represent the lines starting from Q1 and Q3 and using +/- 1.5*IQR to reach an endpoint . The endpoint however is not always at the value reached by solving these equations. What value do you believe MINITAB uses (generally not the values in this example) to determine where to stop these whiskers?