A median is the middle of a data set in order. In a dot plot, the number below a stack is the value, and each dot in the stack is one observation. Count every dot to find the middle position or pair of positions, then read the values there. Counting only the different hour labels can give the wrong middle.
Hints
- Hint 1
In a dot plot, each dot represents one student's study time. Dots stacked above the same hour are separate values. What ordered list do you get if you write that hour once for every dot?
- Hint 2
A median is the middle of an ordered list. When the list has an even number of values, use the two middle positions, not the two middle hour labels on the axis. How many dots are there altogether?
Step-by-step
Count the middle dots
Step 1Write one value for each dot
No Desmos needed. The dot plot shows every study time, so you can count its middle dots directly. Read the hour below each stack and write it once per dot. The three dots above give three entries of :
- Step 2
Locate the middle positions
The list has eight values, so its median, the middle of the ordered data, lies between positions and . Each dot gets its own position, even when several dots have the same value.
- Step 3
Read and average the middle values
The fourth and fifth values are both . With an even number of values, average those two middle values:
So the median study time is hours. Choice C.