Note: continuity correction OK?

Criteria for use of normal approximation
for proportions

Cochran (1977) gives the following minimum values of n for when to use the normal approximation for proportions varying from 0.5 to 0.05:

p or q
whichever is smaller Minimum
n

0.5 30

0.4 50

0.3 80

0.2 200

0.1 600

0.05 1400

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Criteria for use of normal approximation for proportions

Criteria for use of normal approximation
for proportions