1.11. Process of Classification

Once the number of groups and the class interval of each group are determined, the raw data are classified as shown in Table 1.5.

In this step, the classification process begins by first identifying how many groups (or categories) we want to sort our data into. Each group is then assigned a range of values, known as class intervals. For instance, if we are dealing with a set of ages, we might have groups like 0-10, 11-20, and so forth, determining how wide each range will be.

Imagine you are organizing books in a library. You would first decide how to categorize them, perhaps by genre (fiction, non-fiction, mystery) and then how many sections you need within each genre based on the number of books you have.

It is done by a method popularly known as Four and Cross Method or tally marks.

The Four and Cross Method refers to a way of counting occurrences in each group using tally marks. This method is efficient for visual representation of data, allowing us to quickly see how many values fall into each group. Each complete set of four tally marks is crossed over with a fifth mark to represent that group.

Think about keeping score in a game. Instead of writing numbers, you might tally points on paper. After scoring four points, you put a line across those four tallies to ensure easy counting at a glance without confusion.

First of all, one tally mark is assigned to each individual in the group in which it is falling. For example, the first numerical in the raw data is 47. Since, it falls in the group of 40–50, one tally mark is recorded in the column 3 of Table 1.5.

As we examine each number in our raw data, we assign a tally mark to the corresponding group based on where the number falls. Continuing with our example, if the first number is 47, we see that it belongs in the group for values between 40 and 50 and thus, we place one tally mark in the tally column for that group.

Imagine at a carnival where you have to count how many people go on different rides. Each time a person rides, you make a tally mark in that ride's category, helping you keep track of who has enjoyed which ride more efficiently.

Table 1.5: Making Tally Marks to Obtain Frequency

Table 1.5 is a detailed visual representation of how data is organized into groups, represented by ranges and how many entries fall into each range using tally marks. The 'Tally Marks' column shows how many individuals belong to each group visually, while the 'Number of Individual' column gives the exact count. The sum at the bottom shows the total number of items classified.

Consider a pizza restaurant that tracks how many slices of different types of pizza were sold in a day. Each type of pizza corresponds to a tally, and at the end of the day, the restaurant manager counts the tallies to see which pizza was the most popular, similar to how Table 1.5 is used to analyze data.

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