Measures of variability

Question 1

What is the 4 measures of variability

Answer 1

Range, interquartile range, variance and standard deviation

Question 2

How to define range?

Answer 2

The value that represents the difference between the maximum and minimum value of a sample

Question 3

What the quartiles (25,50,75) mean?

Answer 3

It’s the value that below it represents 25,50,75% of others numbers in a sample. 50% is in the middle, for example

Question 4

What are 6 descriptive values that you can see in a box plot?

Answer 4

1,2) Minimum and maximum
3,4,5) Q1 (25%), Q2 or Median (50%), Q3 (75%)
6) Outliers

Question 5

What variance and standard deviation?

Answer 5

Variance is the sum of the difference of every item and the mean divided by the sample. And standard deviation is the square root of variance. A single value to measure the variability of a sample

Question 6

Why do we use n-1 to calculate the variance?

Answer 6

Because usually the sample underestimate the amount of variation a population has. So we decrease the sample value to increase the variance