Question

In a survey, 32 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $42.6 and standard deviation of $11.8. Estimate how much a typical parent would spend on their child's birthday gift (use a 80% confidence level). Give your answers to 3 decimal places.

Express your answer in the format of x +_

$___ +_ $_____

Answer 1

We have given that,          
          
Sample mean =$42.6  
Sample standard deviation =$11.8
Sample size =32  
Level of significance=1-0.80=0.2  
Degree of freedom =31  
          
t critical value is (by using t table)=1.309  
Confidence interval formula by t

Therefore,

$42.6 $ 2.731