How to Summarize Qualitative Data Using Tables & Graphs

Example 2.3. Consider the following customer service times: The twenty numbers in Table 2.9 represent a sample of customer waiting times in a bank. A time of 1 indicates that the customer waited between 0 to 1 minutes before the next teller was available to assist him or her. A value of 3 means the customer waited longer than 2 minutes but no longer than 3 minutes before receiving assistance, etc. Use the three step method listed above to make a frequency distribution. Also include the relative frequency and the percent frequency in your table. Solution. Step one The data set contains twenty values and those values range from 1 to 12 minutes. Since this data set is somewhat small, let's plan on using five classes. Step two We see that the smallest data value is 1 and the largest value is 12. Now use the formula. Step three In step two, we calculated a class width of 2.2. However, since all the values in our data set are integers, our class width should be an integer. Therefore, we will use standard rounding rules for arithmetic and round this the approximate width of 2.2 down to an integer value of 2. So, according to the calculations, the class width should be two. However, one must be flexible using a certain amount of judgment and discretion in selecting the class width. You might find that a class width of two produces too many classes for your application. In that case, you might try a class width of three, or more. We will use two as the first try for the class width. Using 2, we find that the first class will range from 1 - 2, class two ranges from 3 - 4, the third class ranges from 5 - 6 and the fourth class ranges from 7 - 8. For the fifth class, there is an anomaly. If we use the class width 2, then the class would range from 9 - 10. However, there is a 12 in the data set … where do we put it? To fully understand the problem, we need to understand that the issue is a direct result to fact we rounded down a calculated value when making the class width.