Question

A computer manufacturer estimates that its line of minicomputers has, on average, 8.5 days of downtime per year. To test this claim, a researcher contacts seven companies that own one of these computers and is allowed to access company computer records. It is determined that, for the sample, the average number of downtime days is 5.3, with a sample standard deviation of 1.2 days. Assuming that number of downtime days is normally distributed, test to determine whether these minicomputers actually average 8.5 days of downtime in the entire population. Let α = .01.

The value of the Test Statistic is?

Answer 1

using excel>addin>phstat>one sample test

we have

t Test for Hypothesis of the Mean
Data
Null Hypothesis                m=	8.5
Level of Significance	0.01
Sample Size	7
Sample Mean	5.3
Sample Standard Deviation	1.2
Intermediate Calculations
Standard Error of the Mean	0.4536
Degrees of Freedom	6
t Test Statistic	-7.0553
Two-Tail Test
Lower Critical Value	-3.7074
Upper Critical Value	3.7074
p-Value	0.0004
Reject the null hypothesis

The value of the Test Statistic is -7.0553