In: Statistics and Probability
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 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. Use Table 2. (Round your answers to 3 decimal places.)  | 
| tα/2,df | |
| a. A 90% confidence level and a sample of 13 observations. | |
| b. A 95% confidence level and a sample of 13 observations. | |
| c. A 90% confidence level and a sample of 22 observations. | |
| d. A 95% confidence level and a sample of 22 observations. | |