Solution:
p = 0.25
q = 1 - p = 0.75
x = 127
n = 480
psample = x/n = 127/480 = 0.2645
test statistic, z = (psample - p) / sqrt(pq/n) = (0.2645 - 0.25) / sqrt(0.25×0.75/480) = 0.733
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