Statistics Examples
1. Let's consider a problem involving mean (average):
Find the mean of the data set $\{2, 4, 6, 8, 10\}$.
To find the mean, sum all values and divide by the number of values:
$$\text{Mean} = \frac{2+4+6+8+10}{5} = \frac{30}{5} = 6.$$
2. A problem involving median:
Find the median of $\{7, 3, 9, 5, 11\}$.
First, arrange the data in ascending order: $\{3, 5, 7, 9, 11\}$.
Median is the middle value, which is $7$.
3. A problem involving mode:
Find the mode of $\{1, 2, 2, 3, 4, 4, 4, 5\}$.
The mode is the value that appears most frequently, which is $4$.
4. A problem involving variance:
Find the variance of $\{3, 7, 7, 19\}$.
Step 1: Calculate mean: $$\mu = \frac{3+7+7+19}{4} = \frac{36}{4} = 9.$$
Step 2: Calculate squared deviations: $$(3-9)^2 = 36,\ (7-9)^2=4,\ (7-9)^2=4,\ (19-9)^2=100.$$
Step 3: Calculate variance: $$\sigma^2 = \frac{36+4+4+100}{4} = \frac{144}{4} = 36.$$
5. A problem involving standard deviation:
Using the variance above ($36$), standard deviation is the square root: $$\sigma = \sqrt{36} = 6.$$