1. Coffee and Cardiovascular Disease
Is coffee beneficial?

2. Background
The purpose of this significance test is to ultimately assess whether or not coffee truly does reduce the risk of death from cardiovascular disease.
A 20 year study was conducted concerning this matter men participated and women participated. The study was published in the magazine “Annals of Internal Medicine.”
Information about the participants was updated about every 2 years. This is important because age, height, weight, medical history, health status, etc. change as time goes on.
A limitation of this study is that coffee consumption was probably estimated by most of the participants in the study. Slight error due to this basically inevitable.

3. Background
Age, smoking, and other cardiovascular disease factors were adjusted for. This means that these factors were controlled for so the relationship between coffee and cardiovascular disease can be better assessed. Without these factors being adjusted for, the study is useless.

4. Background
These factors were controlled through the use of adjusted relative risk (RR).
Relative risk is a ratio of the probability of an event occurring in the exposed group versus a non-exposed group.

5. Background
An RR>1 means the event of interest is more likely to occur in the “exposed” group.
An RR<1 means the event of interest is less likely to occur in the “non-exposed” group.
An RR=1 means there is no difference in risk between the two groups.

6. Background
In this study, the RR was adjusted to 1 in the factors discussed earlier (age, smoking, parental history, weight, height, history of hypertension, Type II diabetes, etc).
If RR was not adjusted, the study would be useless obviously because older people, smokers, etc. are going to be more at risk for cardiovascular disease.

7. Background
Men and women participant data was separated. Participants were grouped into six categories within the two blocks. The groups were people that drink:
<1 cup of coffee/month
1 cup/month to 4 cups/week
5-7 cups/week
2-3 cups/day
4-5 cups/day
≥6 cups/day

8. Male Data Amount of Coffee # of Participants
# of Cardiovascular Disease Deaths
<1 coffee/month
12168
459
1 cup/month – 4 cups/week
7353
488
5-7 cups/week
7564
664
2-3 cups/day
9968
357
4-5 cups/day
3468 66
≥6 cups/day
1215 15

9. Female Data Amount of Coffee # of Participants
# of Cardiovascular Disease Deaths
<1 coffee/month
19276
362
1 cup/month – 4 cups/week
5264
5-7 cups/week
11672
868
2-3 cups/day
28375
563
4-5 cups/day
14465
151
≥6 cups/day
7162 62

10. Significance Test - Males
H0 : pL = ps
Ha : pL < ps
ps is the proportion of people that die from cardiovascular disease who drank SMALL amounts of coffee
Small amounts of coffee means 0 cups of coffee to 5-7 cups of coffee per week.
pL is the proportion of people that die from cardiovascular disease who drank LARGER amounts of coffee
Larger amounts of coffee means 2 or more cups of coffee per day.

11. Significance Test - Males
Conditions
SRS: The condition of SRS is not established. The sampling method is only mentioned as a random sampling method.
Normality: n1p̂c, n1(1-p̂c), n2p̂c, n2(1-p̂c) are all at least 5.
n is the sample size and p̂c is the combined sample proportion
27085(.0491) > 5, 27085( ) > 5, 14651(.0491) > 5, 14651( ) > 5
Independence: There is no reason to believe that the two samples aren’t independent. There are probably more than 27085(10) = men in the entire population that drink small amounts of coffee. There are probably more than 14651(10) = men in the entire population that drink larger amounts of coffee. There are more than 300 million people in the United States, so yes, this is reasonable.
We will proceed to conduct a two-proportion significance test and interpret at a significance level of .05.

12. Significance Test - Males
Calculations:
p̂L = (heavy coffee drinkers)
p̂s = (light coffee drinkers)
z =
P-value = 0

13. Significance Test - Males
Interpretation:
There is very strong evidence against the null hypothesis, according to the P-value that is practically zero. There is statistically significant evidence against the null hypothesis that the proportion of deaths due to cardiovascular disease is the same in men that drink small amounts of coffee and men that drink larger amounts of coffee. The alternative hypothesis seems more likely, according to these calculations. It is highly likely that the proportion of deaths due to cardiovascular disease in men that drink larger amounts of coffee is less than the proportion of deaths due to cardiovascular disease in men that drink small amounts of coffee.

14. Significance Test - Females
H0 : pL = ps
Ha : pL < ps
ps is the proportion of people that die from cardiovascular disease who drank SMALL amounts of coffee
Small amounts of coffee means 0 cups of coffee to 5-7 cups of coffee per week.
pL is the proportion of people that die from cardiovascular disease who drank LARGER amounts of coffee
Larger amounts of coffee means 2 or more cups of coffee per day.

15. Significance Test - Females
Conditions
SRS: The condition of SRS is not established. The sampling method is only mentioned as a random sampling method.
Normality: n1p̂c, n1(1-p̂c), n2p̂c, n2(1-p̂c) are all at least 5.
n is the sample size and p̂c is the combined sample proportion
36212(.0275) > 5, 36212( ) > 5, 50002(.0275) > 5, 50002( ) > 5
Independence: There is no reason to believe that the two samples aren’t independent. There are probably more than 36212(10) = women in the entire population that drink small amounts of coffee. There are probably more than 50002(10) = women in the entire population that drink larger amounts of coffee. There are more than 300 million people in the United States, so yes, this is reasonable.
We will proceed to conduct a two-proportion significance test and interpret at a significance level of .05.

16. Significance Test - Females
Calculations:
p̂L = (heavy coffee drinkers)
p̂s = (light coffee drinkers)
z =
P-value = 0

17. Significance Test - Females
Interpretation:
There is very strong evidence against the null hypothesis, according to the P-value that is practically zero. There is statistically significant evidence against the null hypothesis that the proportion of deaths due to cardiovascular disease is the same in women that drink small amounts of coffee and women that drink larger amounts of coffee. The alternative hypothesis seems more likely, according to these calculations. It is highly likely that the proportion of deaths due to cardiovascular disease in women that drink larger amounts of coffee is less than the proportion of deaths due to cardiovascular disease in women that drink small amounts of coffee.

18. Additional Information
These results are not surprising.
Coffee causes blood vessels and arteries to become more flexible, which automatically reduces the risk of heart disease.
The older you get, the more important flexible arteries becomes.
Coffee contains antioxidants, which defend against free radicals. Free radicals are oxidizing agents that cause health problems such as cancer, heart disease, and degradation of the immune system.
Coffee also contains methylpyridinum, which is a known anti-cancer compound exclusive to coffee.
Coffee drinkers, on average, live two years longer than people who don’t drink coffee.
Due to all of these benefits from drinking coffee, it is not surprising that these results were obtained from the significance tests conducted.

19. Sources http://www.annals.org/content/148/12/904.full.pdf+html