STA104 WEEK 6

Video V1W6: Coefficient of Variation (CV) 

LEARNING OBJECTIVE 2

Measures of Skewness

Students need to know how to calculate and made correct decision using measure of skewness.

👉🏼 Refer Pg. 48 - 49

👉🏼 Watch Video V2W6

Correction in my YouTube video (V2W6):

Note that, at minute 18:56 until end of the video, there is an accidental mistake where I interpreted the meaning of skewed to the left is "There are more younger tourist as compared to the average age OR There are less older tourist as compared to the average." It is supposed to be the otherwise.

👉🏼 Watch Video V3W6 (extra explanation)

👉🏼 Redo Example (c) Pg. 55

👉🏼 Do Exercise 1(c) Pg. 58

Answer: 

By using formula Pearson coefficient of skewness with info mean and mode:

Skewness = 0.56 (skewed to the right)

It indicates that there are more lower weekly sales as compared to the average weekly sales.

Note: You can use formula with mean and median too since in this example you have mean, median and mode values.

👉🏼 Do Exercise 2(b) Pg. 60

Answer: 

By using formula Pearson coefficient of skewness with info mean and mode:

Class A:  Skewness = 1.67

Class B:  Skewness = 0

Class C:  Skewness = -2  

So, Class A has a distribution skewed to the right.

👉🏼 Redo Example 24 (No.5) Pg. 65 - 66

Extra Note:

There are 2 ways to detect skewness or shape of data distribution for a set of data.

1) Graphical Method

👉🏼 By using stem and leaf plot, histogram and box plot

2) Numerical Method

👉🏼 By calculating Pearson coefficient of skewness

👉🏼 By comparing values of mean, median and mode

Video V2W6: Measures of Skewness