I have collected data that shows the days on which I fasted and if those days resulted in weight-loss.
Null hypothesis:
Data Analysis:
Conclusion (laymen's):
Conclusion (statistical):
My Questions:
Contingency table & data visualization:

Null hypothesis:
There is no statistically significant relationship between fasting and weight loss.
Data Analysis:
1 The chart (see way below) is a visual representation of my data. The circled points indicate a prolonged period of fasting and shows a downward trend in weight (i.e. weight loss occurred) during these periods.
2) The contingency/crosstab table (see below) shows that:
- a) on the days that I fasted weight-loss occurred 93% of the time (100/107).
- b) on the days that I did not fast weight-loss occurred 38% of the time (348/924)
Conclusion (laymen's):
Intuitively, this suggests that there is a high correlation between the days on which I fasted and weight-loss occurring, and though weight-loss can occur on non-fasting days, it happens a lot less than on fasting days (93% vs. 38%).
Conclusion (statistical):
I calculated the phi-coefficient (aka Yule phi or Mean Square Contingency Coefficient) to be -0.343 (see contingency table below for numbers used).
I chose phi-coefficient for my correlation method as my variables are dichotomous (actually dichotomized) and various sources suggest this method is suitable (please note that I am not a statistician and only learnt what the phi-coefficient was yesterday, before this the entirety of experience with correlation was using the CORREL function once in Excel a long time ago).
This source suggests that a phi-coefficient of 0.3-0.39 represents a "moderate" relationship between the variables.
This source (see table 2) suggest that a phi-coefficient of >0.25 represents a "very strong" relationship between the variables.
My Questions:
1) Is my methodology, reasoning and calculation sound? If not how would approach testing my null hypothesis?
2) My phi-coefficient of 0.343 seems low when taking into account my laymen's conclusion (weight-loss on fasting vs. non-fasting days is 93% vs. 38%) - do you agree? why is it so far from a maximum possible value of 1?
Thanks and please let me know if I can clarify anything further!Contingency table & data visualization:

