The American Sugar Producers Association wants to estimate
themean yearly sugar consumption. A sample of n = 12 people
revealsthe mean yearly consuption to be 55 pounds with a
standarddeviation of 20 pounds. Find the lower bound for the 98%
confidenceinterval for the mean yearly sugar consumption. Assume
thepopulation is normal.

Respuesta :

Answer: 39.308 pounds

Step-by-step explanation:

We assume that the given population is normally distributed.

Given : Significance level : [tex]\alpha: 1-0.98=0.02[/tex]

Sample size : n= 12, which is  small sample (n<30), so we use t-test.

Critical value (by using the t-value table)=[tex]t_{n-1, \alpha/2}=t_{11,0.01}=2.718[/tex]

Sample mean : [tex]\overline{x}=50[/tex]  

Standard deviation : [tex]\sigma= 20[/tex]

The lower bound of confidence interval is given by :-

[tex]\overline{x}-t_{(n-1,\alpha/2)}\dfrac{\sigma}{\sqrt{n}}[/tex]

i.e. [tex]55-(2.718)\dfrac{20}{\sqrt{12}}[/tex]

[tex]=55-15.6923803166\approx55-15.692=39.308[/tex]

Hence, the lower bound for the 98%  confidence interval for the mean yearly sugar consumption= 39.308 pounds