Statistics Homework

Question

In a survey, 10 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 $20. Construct a confidence interval at a 80% confidence level.

Give your answers to one decimal place.

Answer 1

z=1.282 for 80%

use z tables or a z calculator

Margin Of Error=

MOE = z(sd)/sqr(n) = 1.282(20)/sqr(10)

=25.64/sqr10

Confidence Interval = mean plus or minus MOE

CI=49+/-25.64/sq10= about 49+/-8.1

=(40.9, 57.1)