Measures of Center

The mean is the average of a set of numbers, calculated by adding all the numbers together and dividing by the total count of numbers.

Add the numbers: 90 + 100 + 95 + 85 + 60 + 80 = 510. Then divide by the count of numbers (6): 510 / 6 = 85.

The median is the middle number in a sorted list of numbers. If there is an even number of observations, the median is the average of the two middle numbers.

First, sort the numbers: 77, 78.5, 80, 99. Since there are 4 numbers (even), the median is the average of the two middle numbers: (78.5 + 80) / 2 = 79.25.

The mode is the number that appears most frequently in a data set.

The mode is 2, as it appears most frequently.

The range is the difference between the highest and lowest values in a data set.

Range = Highest value - Lowest value = 20 - 5 = 15.

A dot plot is a simple way to display data using dots above a number line, where each dot represents one occurrence of a value.

Count the total number of dots. If odd, the median is the middle dot. If even, the median is the average of the two middle dots.