Question

In a survey, 11 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $40.4 and standard deviation of $20.1. Estimate how much a typical parent would spend on their child's birthday gift (use a 90% confidence level). Give your answers to 3 decimal places.

Express your answer in the format of ¯xx¯ ±±  E.
answer $___ ±± $____ answer

Answer 1

Solution :

df = 11 - 1 = 10

t _/2,df = 1.812

Margin of error = E = t_/2,df * (s /n)

= 1.812 * (20.1 / 11)

Margin of error = E = 10.984

The 95% confidence interval estimate of the population mean is,

E = $40.4 $ 10.984