Question

In a survey, 16 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $33 and standard deviation of $4. Construct a confidence interval at a 80% confidence level.

Answer 1

Solution :

t _/2,df = 1.341

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

= 1.341 * (4 / 16)

Margin of error = E = 1.34

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

- E < < + E

33 - 1.34 < < 33 + 1.34

31.66 < < 34.34

(31.66 , 34.34)