According to the website ww.costofwedding.com, the average cost of flowers for a wedding is $698. Recently, in a random sample of 40 weddings in the U.S. it was found that the average cost of the flowers was $734, with a standard deviation of $102. On the basis of this, a 95% confidence interval for the mean cost of flowers for a wedding is $701 to $767.
For this description, which of the following does not describe a condition for a valid confidence interval?
◦ The sample observations are independent because knowledge about the cost of flowers for any one wedding tells us nothing about the cost of flowers for any other wedding in the sample.
◦ All of these describe conditions for a valid confidence interval.
◦ The description states that the sample was randomly selected, so we can assume that the condition which states that the data must represent a random sample is satisfied.
◦ The sample size of 40 is large enough that knowledge about the population distribution is not necessary and the condition that the population be normally distributed or sample size be larger than 25 is satisfied.
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