Hours of sleep — n = 7
Last night, seven friends each wrote down how many hours they slept. Let's summarize what they found.
Here are their numbers: six, seven, eight, eight, eight, nine, and ten hours.
We can plot each value as a dot above a number line. Each dot stands for one student's hours of sleep.
First, we count the observations. There are seven dots, so n equals seven — all measured in hours of sleep.
The values are already in order. With seven numbers, the fourth is the middle. The median is eight hours.
For the mean, we add every value, then divide by n. The sum is fifty-six, and fifty-six divided by seven equals eight. The mean is eight hours.
For variability, the range is the highest value minus the lowest. Ten minus six equals four. The range is four hours.
Putting it back in context: a typical student in our class sleeps about eight hours, and the amounts vary by four hours across the group.
Our complete summary: seven students, hours of sleep, mean and median both eight, range four. That is a full data summary!
Now you try. Find the value with the tallest stack. Which value is most common?