Data Handling - Tally Marks

Data Collection: Data is a collection of facts, such as numbers, words, measurements, or observations, gathered together to provide information. In a classroom, recording students' favorite fruits is a form of data collection.

Definition of Tally Marks: Tally marks are a quick and easy way of recording and counting data. Instead of writing numbers repeatedly, we use vertical lines ($|$) to represent each item counted.

The Group of Five: Tally marks are organized in groups of five to make counting faster. We draw four vertical lines ($| | | |$), and the fifth line is drawn diagonally across the four vertical lines to create a 'bundle' or group of 5. Visually, it looks like four standing sticks tied together by a slanted stick.

Frequency: Frequency refers to the total number of times a particular item or event occurs in the data. In a table, the frequency is written as a number (e.g., $5$, $12$, $3$) next to the tally marks.

Tally Table Structure: A tally table is usually organized into three columns. The first column lists the 'Category' or 'Items', the second column shows the 'Tally Marks', and the third column displays the 'Frequency' or 'Number of Items'.

Counting Strategy: To find the total frequency from tally marks, we count the bundles by $5s$ and then add the individual lines that follow. For example, two bundles and three lines are counted as $5 + 5 + 3 = 13$.

Representation of Numbers: Single numbers are represented by simple vertical strokes. For instance, the number $3$ is shown as $|||$ and the number $4$ as $||||$. Once we reach $5$, we must use the diagonal crossing line.