Before you read

Answer first — see what you already know.

A histogram displays the ages of 50 visitors at a science museum. The bins and frequencies are: 0-10 (8), 10-20 (15), 20-30 (12), 30-40 (10), 40-50 (5). What percentage of visitors are under 20 years old?

A
23%
B
30%
C
54%
D
46%

Check your answer

Answer:

Before you read

Answer first — see what you already know.

A dot plot shows the number of pets owned by students in a class:
• 0 pets: ●●●
• 1 pet: ●●●●●●
• 2 pets: ●●●●●
• 3 pets: ●●
• 4 pets: ●
What is the median number of pets?

A
1
B
2.5
C
1.5
D
2

Check your answer

Answer:

Theory

Types of Graphs on the SAT

Bar chart: Compares categories. Read heights of bars.

Bar chart: compare values across categories

Line graph: Shows trends over time. Focus on slopes (increasing/decreasing).

Histogram: Shows distribution of continuous data in intervals (bins). Height = frequency.

Dot plot: Each dot = one data point. Easy to find mode, median, range.

Pie chart (circle graph): Shows proportions of a whole. Each slice is a percentage of 360 $^{\circ}$ .

Example 1

A histogram shows test scores: 60-70 (5 students), 70-80 (12 students), 80-90 (8 students), 90-100 (3 students). How many students scored below 80?

Below 80: bins 60-70 and 70-80

$5 + 12 = 17$ students

17 students

Theory

Reading Graphs Carefully

Always check:
1. Axis labels: What does each axis represent? What are the units?
2. Scale: Does the axis start at 0? Non-zero starts can exaggerate differences.
3. Title: What is the graph about?
4. Intervals: Are histogram bins equal width?

Interpolation: Estimating a value between known data points.
Extrapolation: Estimating beyond the data range (less reliable).

Continue this lesson in the app

2 more sections including examples, practice problems, and step-by-step solutions.

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