We are given a survey of students from
Lincoln School and
Washington School, where 300 students were randomly selected from each school. The table shows how many students from each school reported having 0, 1, 2, 3, or 4 siblings.
We are asked to find the
median number of siblings for
all the students surveyed (i.e., the 600 students: 300 from Lincoln + 300 from Washington).
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Step 1: Understand what the median is
The
median is the middle value when all values are arranged in order.
Since we have
600 students, the median will be the average of the
300th and
301st values when sorted by number of siblings.
So, we need to determine how many students have 0, 1, 2, etc. siblings
in total across both schools, then find which sibling count includes the 300th and 301st students.
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Step 2: Combine the data from both schools
Let’s add up the number of students from both schools for each number of siblings:
| Number of Siblings | Lincoln | Washington | Total |
|--------------------|---------|------------|-------|
| 0 | 120 | 140 | 260 |
| 1 | 80 | 110 | 190 |
| 2 | 60 | 30 | 90 |
| 3 | 30 | 10 | 40 |
| 4 | 10 | 10 | 20 |
|
Total | 300 | 300 | 600 |
Now, let’s compute cumulative totals to find where the 300th and 301st students fall.
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Step 3: Cumulative frequency
| Siblings | Frequency | Cumulative Frequency |
|----------|-----------|----------------------|
| 0 | 260 | 260 |
| 1 | 190 | 260 + 190 = 450 |
| 2 | 90 | 450 + 90 = 540 |
| 3 | 40 | 540 + 40 = 580 |
| 4 | 20 | 580 + 20 = 600 |
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Step 4: Find the median
We want the
300th and
301st students in the ordered list.
- The first
260 students have
0 siblings.
- The next
190 students (from 261 to 450) have
1 sibling.
So:
- The
261st to
450th students have
1 sibling.
Therefore:
- The
300th student has
1 sibling
- The
301st student also has
1 sibling
So the median is the average of the 300th and 301st values:
$$
\text{Median} = \frac{1 + 1}{2} = 1
$$
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✔ Final Answer: B) 1
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> Note: The total number of students at each school (2,400 and 3,300) is
not needed here because we're only analyzing the
surveyed sample of 300 from each school. The question asks about the
students surveyed, not the entire population.
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✔️ Answer: B) 1
Parent Tip: Review the logic above to help your child master the concept of mean median mode questions.