A median is the middle observation once the data are in order, and a dot plot already orders them from left to right. Count every dot, including those stacked above the same time, then find the middle dot. The middle tick mark isn't necessarily the middle observation.
Hints
- Hint 1
In a dot plot, each dot represents one student's time. A stack means that time occurs more than once. Read from left to right, writing the time once for every dot above it.
- Hint 2
The median is the middle observation, not the middle labeled tick. With an odd number of dots, one dot has the same number of observations on each side. Which time does it represent?
Step-by-step
Count to the middle dot
Step 1Write the times in order
No Desmos needed. The dot plot already puts the times in order. Each dot is one student, so the two dots above give two s, and the three above give three s. Reading left to right gives .
- Step 2
Find the middle position
The median is the middle time in the ordered list. There are nine times, so four lie on either side of the fifth time. Count dots, not tick marks. Repeated times each take a position.
- Step 3
Read the fifth time
The is first, the two s are second and third, and is fourth. The fifth time is , so the median walking time is minutes. Choice B.