In: Statistics and Probability
A research firm conducted a survey to determine the mean amount steady smokers spend on cigarettes during a week. They found the distribution of amounts spent per week, followed the normal distribution with the standard deviation of $5. A sample of 49 steady smokers reveal that mean=20.
a). What is the point estimate of the population mean? explain what it indicates
b). using the 95% level of confidence. determine the confidence interval for sample mean. explain what it indicates
Given :-
Standard deviation ( ) = 5,
Sample mean ( ) = 20
Sample size (n) = 49
a)
Therefore the point estimate of the population mean () is equal to sample mean = 20
b)
95% confidence level at alpha=5% then Zc = 1.96
Therefore confidence interval for mean is,
= ( Zc * )
= ( 20 1.96 * ( ) )
= ( 20 1.4 )
=> ( 20 - 1.4) < < ( 20 + 1.4)
18.6 < < 21.4
Therefore, the 95% confident that mean is lies between
( 18.6 , 21.4 ).