In: Math
The USA Today reports that the average expenditure on Valentine's Day is $100.89. Do male and female consumers differ in the amounts they spend? The average expenditure in a sample survey of 40 male consumers was $135.67, and the average expenditure in a sample survey of 35 female consumers was $68.64. Based on past surveys, the standard deviation for male consumers is assumed to be $39, and the standard deviation for female consumers is assumed to be $20.
Solution:
Given:
Male:
Sample size =n1 = 40
Sample mean =
Population Standard Deviation =
Female:
Sample size =n2 = 35
Sample mean =
Population Standard Deviation =
Part a) the point estimate of the difference between the population mean expenditure for males and the population mean expenditure for females
Part b) At 99% confidence, what is the margin of error
Zc is z critical value for c = 0.99 confidence level.
Find Area = ( 1+c)/2 = ( 1 + 0.99 ) / 2 = 1.99 /2 = 0.9950
Thus look in z table for Area = 0.9950 or its closest area and find corresponding z critical value.
From above table we can see area 0.9950 is in between 0.9949 and 0.9951 and both are at same distance from 0.9950, Hence corresponding z values are 2.57 and 2.58
Thus average of both z values is 2.575
Thus Zc = 2.575
Thus
Part c) Develop a 99% confidence interval for the difference between the two population means:
we have:
thus
Thus a 99% confidence interval for the difference
between the two population means is: