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Problem: A sampling observation will be conducted regarding the travels abroad of
Bulgarian citizens according to several characteristics. One of them concerns the period of
stay in other countries. The observation will be done in the course of three months. In is
known that in the course of a quarter (three months) the citizens make about 1 million travels
abroad. From previous observations it is known that the variance of the stay abroad is =
260.
Required:
How large the sampling should be (the number of surveyed people) in order to make an
estimation with a maximum error of 2 (Δx) with confidence probability of 0.95?
Indication:
Since the sampling is a no-return one, use the formula:
Since the given confidence interval is 0,95, z = 1.96.