Raw numbers in a list are hard to read. Today we build two powerful tools that reveal patterns instantly.
Your teacher is building a number line on the board. Each student gets a sticky dot and places it at their assigned score.
Watch what happens as more dots go up. What do you notice?
You just built a line plot — together!
A line plot (dot plot) shows how often each value appears on a number line. Each X or dot = one data point.
Two dots at 74 means two students scored 74. The plot shows frequency at a glance!
Today's data set — 20 quiz scores:
On your worksheet: plot each score on the number line grid. Stack dots above each value. Then answer the cluster/range questions. ⏱ 12 minutes
A stem-and-leaf plot organizes numbers by splitting each into a stem (tens digit) and a leaf (ones digit).
Each leaf is one data value. The row with the most leaves shows where data clusters.
Always sort your data first! It makes the leaf rows come out in order automatically.
Use the same 20 scores. One partner reads the values in order, the other writes the leaves.
⏱ 12 minutes for building + comparison questions
From our data set (63–93), answer in your head:
What is the range? (93 − 63 = ?)
How many scores are in the 80s?
No pencils! Raise your hand when you have both answers.
Both plots use the same data — but each reveals something slightly different. Good data scientists choose the right tool for the question.
Any time you want to understand "where does most of the data fall?" — a line plot or stem-and-leaf is your first move.
🔮 Coming up — Session 5: Now we can see the data's shape. Next we'll calculate the averages — mean, median, mode, and range.