Descriptive Statistics is the branch of statistics that focuses on collecting, organizing, summarizing, and presenting data in a meaningful way.
Example 1: Calculate the Mean, Median, and Mode for the following series: {4, 8, 9, 10, 6, 12, 14, 4, 5, 3, 4}
Solution:
First, we are going to calculate the mean.
Mean = ÎĢx / n
= (4 + 8 + 9 + 10 + 6 + 12 + 14 + 4 + 5 + 3 + 4)/11
= 79 / 11
= 7.1818Thus, the Mean is 7.1818.
Now, we are going to calculate the median.
Arrange the provided data collection in ascending order: 3, 4, 4, 4, 5, 6, 8, 9, 10, 12, 14
Median = [(n + 1) / 2]th term
= [(11 + 1) / 2]th term
= 6th term
= 6
Thus, the median is 6.Now, we are going to calculate the mode.
Mode = The most repeated observation in the dataset
= 4Thus, the mode is 4.
Example 2: Calculate the Range for the following series: {4, 8, 9, 10, 6, 12, 14, 4, 5, 3, 4}
Solution:
Arrange the provided data series in ascending order: 3, 4, 4, 4, 5, 6, 8, 9, 10, 12, 14
Range = H - L
= 14 - 3
= 11So, the range is 11.
Example 3: Calculate the standard deviation and variance of the following data: {12, 24, 36, 48, 10, 18}
Solution:
First we are going to compute standard deviation. For standard deviation calculate the mean, deviation from mean and squared deviation.
Series | Deviation from Mean | Squared Deviation |
|---|---|---|
12 | 12-24.66 = -12.66 | 160.28 |
24 | 24-24.66 = -0.66 | 0.436 |
36 | 36-24.66 = 11.34 | 128.595 |
48 | 48-24.66 = 23.34 | 544.76 |
10 | 10-24.66 = -14.66 | 214.92 |
18 | 18-24.66 = -6.66 | 44.36 |
Mean = 148/6 = 24.66 | sum = 0 | Sum = 1093.351 |
Dividing squared deviation with N-1 => 1093.351 / 5 = 218.67
â(218.67) = 14.79
So, the standard deviation is 14.79.Now we are going to calculate the variance.
s = 14.79
s2 = 218.744So, the variance is 218.744
Practice Problem Based on Descriptive Statistics
Question 1. What is the mean of the data set {4, 8, 9, 10, 6, 12, 14, 4, 5, 3, 4}?
Question 2. What is the median of the data set {4, 8, 9, 10, 6, 12, 14, 4, 5, 3, 4}?
Question 3. What is the mode of the data set {4, 8, 9, 10, 6, 12, 14, 4, 5, 3, 4}?
Question 4. What is the range of the data set {4, 8, 9, 10, 6, 12, 14, 4, 5, 3, 4}?
Question 5. What is the standard deviation of the data set {12, 24, 36, 48, 10, 18}?
Question 6. What is the variance of the data set {12, 24, 36, 48, 10, 18}?
Question 7. What is the quartile deviation formula in descriptive statistics?
Question 8. Write the formula that shows the relationship between the mean, median, and mode in a normal distribution.
Answer:-
- 7.18
- 6
- 4
- 11
- 14.79
- 218.74
- (Q3 - Q1 ) / 2
- Mean - Mode = 3(Mean - Median)