Decision-Based Learning -Null hypothesis for Kruskal Wallis Test

1. Null-hypothesis for Kruskal-
Wallis Test (Conceptual)
Explain

2. To illustrate how to write a null-hypothesis for a
Kruskal-Wallis Test, let’s consider the following
example:

3. Problem #1

4. A pizza café owner wants to know who eats
more slices of pizza: football, basketball, or
soccer players.

5. A pizza café owner wants to know who eats
more slices of pizza: football, basketball, or
soccer players. With this information she will
determine how much inventory she needs
during football and basketball seasons.

6. A pizza café owner wants to know who eats
more slices of pizza: football, basketball, or
soccer players. With this information she will
determine how much inventory she needs
during football and basketball seasons. She asks
you to set up a study, collect the data, run the
analysis and interpret the results for her.

7. A pizza café owner wants to know who eats
more slices of pizza: football, basketball, or
soccer players. With this information she will
determine how much inventory she needs
during football and basketball seasons. She asks
you to set up a study, collect the data, run the
analysis and interpret the results for her. After
collecting the data you realize that there are
some extreme outliers among basketball players
that may skew the results.

8. A pizza café owner wants to know who eats
more slices of pizza: football, basketball, or
soccer players. With this information she will
determine how much inventory she needs
during football and basketball seasons. She asks
you to set up a study, collect the data, run the
analysis and interpret the results for her. After
collecting the data you realize that there are
some extreme outliers among basketball players
that may skew the results. You determine to run
a Kruskal-Wallis Test. How would you state the
null-hypothesis?

9. Null Hypothesis for a KruskalWallis Test

10. Null Hypothesis for a KruskalWallis Test
There is no statistically significant difference
between the Median slices of pizza eaten byby
football, basketball, and soccer players.

11. It’s time to practice:

12. Read the problem that follows and verbalize in your
mind what the null-hypothesis would be

13. The effectiveness of advertising for three products
(Brand X, Brand Y, and Brand Z) was compared.

14. The effectiveness of advertising for three products
(Brand X, Brand Y, and Brand Z) was compared.
Market research at a local shopping center was carried
out, with the participants being shown advertisements
for three brands of soda, which they then rated on the
overall likelihood that they would buy the product (out
of 10, with 10 being "definitely going to buy the
product").

15. The effectiveness of advertising for three products
(Brand X, Brand Y, and Brand Z) was compared.
Market research at a local shopping center was carried
out, with the participants being shown advertisements
for three brands of soda, which they then rated on the
overall likelihood that they would buy the product (out
of 10, with 10 being "definitely going to buy the
product").
1/3 of the participants gave ratings for Brand X , 1/3
gave ratings for Brand Y , and a final 1/3 of the
participants gave ratings for Brand Z.

16. Here is the data set:

17. Brand "X" Brand "Y" Brand "Z"
Participant Rating Participant Rating Participant Rating
1 3 7 1 13 10
2 4 8 2 14 9
3 2 9 1 15 9
4 6 10 1 16 10
5 2 11 3 17 8
6 5 12 2 18 10

18. Template

19. There is no statistically significant difference between
the median [insert dependent variable] by [insert first
level of the independent variable], [insert second level
of the independent variable], and [insert third level of
the independent variable].

20. How would you state the null-hypothesis for this
problem using this particular template?

21. The effectiveness of advertising for three products (Brand X,
Brand Y, and Brand Z) were compared. Market research at a
local shopping center was carried out, with the participants
being shown advertisements for three brands of soda, which
they then rated on the overall likelihood that they would buy
the product (out of 10, with 10 being "definitely going to buy
the product"). 1/3 of the participants gave ratings for Brand X ,
1/3 gave ratings for Brand Y , and a final third of the
participants gave ratings for Brand Z.
There is no statistically significant difference between the
median [insert dependent variable] by [insert first level of
the independent variable], [insert second level of the
independent variable], and [insert third level of the
independent variable].

22. The effectiveness of advertising for three products (Brand X,
Brand Y, and Brand Z) were compared. Market research at a
local shopping center was carried out, with the participants
being shown advertisements for three brands of soda, which
they then rated on the overall likelihood that they would buy
the product (out of 10, with 10 being "definitely going to buy
the product"). 1/3 of the participants gave ratings for Brand X ,
1/3 gave ratings for Brand Y , and a final third of the
participants gave ratings for Brand Z.
There is no statistically significant difference between the
median [insert dependent variable] by [insert first level of
the independent variable], [insert second level of the
independent variable], and [insert third level of the
independent variable].

23. The effectiveness of advertising for three products (Brand X,
Brand Y, and Brand Z) were compared. Market research at a
local shopping center was carried out, with the participants
being shown advertisements for three brands of soda, which
they then rated on the overall likelihood that they would buy
the product (out of 10, with 10 being "definitely going to buy
the product"). 1/3 of the participants gave ratings for Brand X ,
1/3 gave ratings for Brand Y , and a final third of the
participants gave ratings for Brand Z.
There is no statistically significant difference between the
median likelihood to buy the product by [insert first level
of the independent variable], [insert second level of the
independent variable], and [insert third level of the
independent variable].

24. The effectiveness of advertising for three products (Brand X,
Brand Y, and Brand Z) were compared. Market research at a
local shopping center was carried out, with the participants
being shown advertisements for three brands of soda, which
they then rated on the overall likelihood that they would buy
the product (out of 10, with 10 being "definitely going to buy
the product"). 1/3 of the participants gave ratings for Brand X ,
1/3 gave ratings for Brand Y , and a final third of the
participants gave ratings for Brand Z.
There is no statistically significant difference between the
median likelihood to buy the product by [insert first level
of the independent variable], [insert second level of the
independent variable], and [insert third level of the
independent variable].

25. The effectiveness of advertising for three products (Brand X,
Brand Y, and Brand Z) were compared. Market research at a
local shopping center was carried out, with the participants
being shown advertisements for three brands of soda, which
they then rated on the overall likelihood that they would buy
the product (out of 10, with 10 being "definitely going to buy
the product"). 1/3 of the participants gave ratings for Brand X ,
1/3 gave ratings for Brand Y , and a final third of the
participants gave ratings for Brand Z.
There is no statistically significant difference between the
median likelihood to buy the product by Brand X, [insert
second level of the independent variable], and [insert
third level of the independent variable].

26. The effectiveness of advertising for three products (Brand X,
Brand Y, and Brand Z) were compared. Market research at a
local shopping center was carried out, with the participants
being shown advertisements for three brands of soda, which
they then rated on the overall likelihood that they would buy
the product (out of 10, with 10 being "definitely going to buy
the product"). 1/3 of the participants gave ratings for Brand X ,
1/3 gave ratings for Brand Y , and a final third of the
participants gave ratings for Brand Z.
There is no statistically significant difference between the
median likelihood to buy the product by Brand X, Brand Y,
and [insert third level of the independent variable].

27. The effectiveness of advertising for three products (Brand X,
Brand Y, and Brand Z) were compared. Market research at a
local shopping center was carried out, with the participants
being shown advertisements for three brands of soda, which
they then rated on the overall likelihood that they would buy
the product (out of 10, with 10 being "definitely going to buy
the product"). 1/3 of the participants gave ratings for Brand X ,
1/3 gave ratings for Brand Y , and a final third of the
participants gave ratings for Brand Z.
There is no statistically significant difference between the
median likelihood to buy the product by Brand X, Brand Y,
and Brand Z.

28. for Brand X , 1/3 gave ratings for Brand Y , and a final third of
the participants gave ratings for Brand Z.
There is no statistically significant difference between the
median likelihood to buy the product by Brand X, Brand Y,
and Brand Z.