Using t-test, there isn't an enough evidence to support our claim that investment average is $135,000 at α = 0.05.
What is t - test?
The one sample t test compares the mean of your sample data to a known value (population mean in our question, i.e. , we wish to compare the sample mean with the population mean). One sample t test should be used when you the population standard deviation is not known or the sample size is very small.
Assumptions of the t-test for the test to be valid:-
- Data is collected randomly. For example, with simple random sampling.
- The data is approximately normally distributed.
Null hypothesis: μ = $143,260
Alternative hypothesis: μ < $143,260
Calculating test statistic.
n = 30
sample mean = $135,000
sample standard deviation = $30,000
[tex]t_{0} = \frac{sample\ mean - population\ mean}{\frac{standard\ deviation}{\sqrt{sample\ size} } }[/tex]
[tex]t_{0} = \frac{135000 - 143260}{\frac{30000}{\sqrt{30} } }[/tex]
|to| = 1.508
Test criteria:
level of significance = 0.05
t(0.05, 29) = 1.6991
Since, |to| = 1.508 < t(0.05, 29) = 1.6991, null hypothesis cannot be rejected.
Learn more about t-test here
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