Question

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 $35 and standard deviation of $17. Construct a confidence interval at a 95% confidence level.

Answer 1

Answer:

CI  95 %  =  (  28.92  ;  41.08 )

Step-by-step explanation:

Sample Information:

sample size    n  =  30

sample mean  =  35 %

sample standard deviation   s = 17

To construct a CI  95 %

significance level is    α  = 5 %   α = 0.05      α/2  =  0.025

z critical for α/2 from z- table is :   z (c) = 1.96

CI  95 %  =  (  x  ±  z(c) * s/√n )

CI  95 %  =  (  35 ± 1.96 * 17/√30 )

CI  95 %  =  (  35 ±  6.08 )

CI  95 %  =  (  28.92  ;  41.08 )