In: Economics
Faced with rising fax costs a firm issues a guideline that transmissions of 10 pages or more should be sent by 20day mail instead. Exceptions are allowed but they want an average to be 10 or below. The firm examined 35 randomly chosen fax transmissions during the next year, yielding a sample mean of 14.44 pages with a standard deviation of 4.45 pages.
a. At the .01 level of significance, is the true mean greater than 10?
b. Use the table posted on blackboard to find the right-tail pvalue
Hypothesis Test for mean:
Assuming you have a large enough sample such that the central limit
theorem holds, or you have a sample of any size from a normal
population with known population standard deviation, then to test
the null hypothesis
H0: µ = ? or
H0: µ = ? or
H0: µ = ?
Find the test statistic z = (xbar - ? ) / (sx / v (n))
where xbar is the sample average
sx is the sample standard deviation, if you know the population
standard deviation, s , then replace sx with s in the equation for
the test statistic.
n is the sample size
The p-value of the test is the area under the normal curve that is
in agreement with the alternate hypothesis.
H1: µ > ?; p-value is the area to the right of z
H1: µ < ?; p-value is the area to the left of z
H1: µ ? ?; p-value is the area in the tails greater than |z|
If the p-value is less than or equal to the significance level a,
i.e., p-value = a, then we reject the null hypothesis and conclude
the alternate hypothesis is true.
If the p-value is greater than the significance level, i.e.,
p-value > a, then we fail to reject the null hypothesis and
conclude that the null is plausible. Note that we can conclude the
alternate is true, but we cannot conclude the null is true, only
that it is plausible.
The hypothesis test in this question is:
H0: µ = 10 vs. H1: µ > 10
The test statistic is:
z = ( 14.44 - 10 ) / ( 4.45 / v ( 35 ))
z = 5.902785
The p-value = P( Z > z )
= P( Z > 5.902785 )
= 1.787077e-09
Since the p-value is less than the significance level we reject the
null hypothesis and conclude the alternate hypothesis µ > 10 is
true.
What do you think