We use the t distribution for the statistical inference of 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. use table 2. (round your answers to 3 decimal places.) tα/2,df
a. a 90% confidence level and a sample of 28 observations.
b. a 95% confidence level and a sample of 28 observations.
c. a 90% confidence level and a sample of 15 observations.
d. a 95% confidence level and a sample of 15 observations