A cross-sectional study among rural residents of one town in Bangladesh looked a
ID: 3364568 • Letter: A
Question
A cross-sectional study among rural residents of one town in Bangladesh looked at the association between the level of arsenic in the well water of each household and the presence of high blood pressure in the head of the household. The SPSS results are below. What is the best interpretation of these results?
Blood Pressure (bp)
Total
0
Normal
1
High
Water contaminated with arsenic
0. No arsenic
Count
119
28
147
Expected Count
93.6
53.4
147
% within arsenic water contaminated with arsenic
81%
19%
100%
1. Arsenic
Count
23
53
76
Expected Count
48.4
27.6
76
% within arsenic water contaminated with arsenic
30.3%
69.7%
100%
Total
Count
142
81
223
Expected Count
142.0
81
223
% within arsenic water contaminated with arsenic
63.7%
36.3%
100%
Chi-Square Tests
Value
df
Asymp. Sig.
(2-Sided)
Exact Sig.
(2-Sided)
Exact Sig.
(1-Sided)
Pearson Chi-Square
55.654(b)
1
0.000
Continuity Correction(a)
53.484
1
0.000
Likelihood Ratio
55.903
1
0.000
Fisher's Exact Test
0.000
0.000
Linear-by-Linear Association
55.404
1
0.000
N of Valid Cases
223
aComputed only for a 2 × 2 table
b0 cells (0.0%) have expected count less than 5. The minimum expected count is 27.61.
A.
Those with arsenic in their well are significantly more likely to have high blood pressure compared to those without arsenic in their well.
B.
Those with arsenic in their well are more likely to have high blood pressure compared to those without arsenic in their well, but the association is not statistically significant.
C.
Those with arsenic in their well are significantly less likely to have high blood pressure compared to those without arsenic in their well.
D.
Those with arsenic in their well are less likely to have high blood pressure compared to those without arsenic in their well, but the association is not statistically significant.
The same study among rural Bangladeshis also looked at the association between arsenic in the well and obesity. The SPSS results are below. Which p-value should the investigators report?
Obese
Total
0
Not obese
1
obese
Arsenic water contaminated with arsenic
0 No arsenic
Count
146
1
147
Expected count
145
2
147
% within arsenic water contaminated with arsenic
99.3%
0.7%
100%
1 Arsenic
Count
74
2
76
Expected count
75
1
76
% within arsenic water contaminated with arsenic
97.4%
2.6%
100%
Total
Count
220
3
223
Expected count
220
3
223
% within arsenic water contaminated with arsenic
98.7%
1.3%
100%
Chi-Square Tests
Value
df
Asymp. Sig.
(2-Sided)
Exact Sig.
(2-Sided)
Exact Sig.
(1-Sided)
Pearson Chi-Square
1.437(b)
1
0.231
Continuity Correction(a)
0.343
1
0.558
Likelihood Ratio
1.340
1
0.247
Fisher's Exact Test
0.268
0.268
Linear-by-Linear Association
1.431
1
0.232
N of Valid Cases
223
aComputed only for a 2 × 2 table
b2 cells (50.0%) have expected count less than 5. The minimum expected count is 1.02.
A.
The Fisher's exact p-value = 0.268.
B.
The likelihood ratio = 1.340.
C.
The chi-square statistic = 1.437.
D.
The chi-square p-value = 0.231.
Blood Pressure (bp)
Total
Explanation / Answer
First part
Answer is (A) Those with arsenic in their well are significantly more likely to have high blood pressure compared to those without arsenic in their well
Note : since p value for chi square test is very low ( asym. Sig , two sided = 0.000) the result is significant, ( p value < 0.05 is considered to be significant)
Also since there are zero cells with expected frequencies less than 5 , chi square test is applied here
Second part
Answer is (A) fishers exact p value = 0.268
Note : since two cells have expected frequencies less than 5 , fishers exact test is appropriate here
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