FAQ: Hypothesis Testing - Chi Square Test


#1

This community-built FAQ covers the “Chi Square Test” exercise from the lesson “Hypothesis Testing”.

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This exercise can be found in the following Codecademy content:

Data Science

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#2

Can someone explain me what exactly is the null-hypotesis in this exercise please?


#3

As I got it, Null hepothesis always is a statment, that any difference between sets of data is accidental. So, if a result of test is less then 0.05 (5%), you can reject Null hepothesis, and state, that there is a difference.


#4

I don’t understand. How can p be so big (= 0.155082308077) for this table:

# Contingency table
#         harvester |  leaf cutter
# ----+------------------+------------
# 1st gr | 30       |  10
# 2nd gr | 35       |  5
# 3rd gr | 28       |  12

when there are visibly extreme differences between harvester and leaf cutter, while at the same time it’s so small (p = 0.00281283455955) for this table:

# Contingency table
#         harvester |  leaf cutter
# ----+------------------+------------
# 1st gr | 30       |  10
# 2nd gr | 35       |  5
# 3rd gr | 28       |  12
# 4th gr | 20       |  20

after we added an equal amount of ants to both columns, which should even things out and therefore increase the probability of there not being a major difference between these sets.