SOLUTION: In a survey, 30 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $49 and standard deviation of $7. Con

Question 1170281: In a survey, 30 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $49 and standard deviation of $7. Construct a confidence interval at a 80% confidence level.
Give your answers to one decimal place.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
half-interval is t(0.90, df=29)*s/sqrt(n)
=1.311*7/sqrt(30)
=1.675
CI is mean+/- half-interval or
($47.325, $50.675) Or ($49.3, $50.7)
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