A step on from this range is the interquartile range. This is the difference between the first quartile and the third quartile - giving us the middle 50% of observations. To work out the first quartile, we take N (number of observations) and divide it by 4. This will give us the number of the observation at which the first quartile point is. To work out the third quartile we take N and divide it by 4 and then multiply the result by 3. This gives us the number of the observation at which the third quartlile mark is. From there, we just subtract the value of the first quartile figure away from the third quartile figure.
The quartiles are then displayed on a box plot diagram. A box plot will look generally as follows:
- Mean Deviation = (Σ|Xi - x̄|) / n
- Xi = each observation
- x̄ = the sample mean.
- n = number of observations.
- Population variance = (Σ|X - μ|)^2 / N
- Sample variance = (Σ|Xi - x̄|)^2 / (n - 1)
Thanks for reading, have a good day.