A phycologist is worried that a large proportion of the algae found in nearby water sources is cyanobacteria. He obtains a random sample of 50 alga from a local river and another random sample of size 75 from the local coastline. He finds that 22 of the river samples and 66 of the coastline samples are cyanobacteria. Let p1 and p2 represent the proportion of cyanobacteria in river and coastal populations, respectively. Calculate a 95% confidence interval for p1  p2.
a. 
0.44 ± 0.1560 

b. 
–0.44 ± 0.1309 

c. 
–0.44 ± 0.1371 

d. 
–0.44 ± 0.2050 

e. 
–0.44 ± 0.1634 
option A is right
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