Question 1162936: We use the t distribution to construct a confidence interval for the population mean when the underlying population standard deviation is not known. Under the assumption that the population is normally distributed, find tα/2,df for the following scenarios. (You may find it useful to reference the t table. Round your answers to 3 decimal places.)
tα/2,df
a. A 95% confidence level and a sample of 18 observations.
b. A 99% confidence level and a sample of 18 observations.
c. A 95% confidence level and a sample of 9 observations.
d. A 99% confidence level and a sample of 9 observations.
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! the critical t-score will be as follows:
with 18 observations, the degrees of freedom = 17
with 9 observations, the degrees of freedom = 8
i used the following table:
https://www.sjsu.edu/faculty/gerstman/StatPrimer/t-table.pdf
at 95% confidence level, the two tail critical t-score will be 2.306 with 8 degrees of freedom and 2.110 with 17 degrees of freedom.
at 99% confidence level, the two tail critical t-score will be 3.355 with 8 degrees of freedom and 2.898 with 17 degrees of freedom.
note that the two tail critical t-score at .05 is the same as the one tail critical t-score at .025 and the two tail critical t-score at .01 is the same as the one tail critical t-score at .005.
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