Determine the t-percentile that is required to construct each of the following two-sided confidence intervals:

1. Confidence level = 95%, degrees of freedom = 20
2. Confidence level = 99%, degrees of freedom = 20
3. Compare the two t-percentile values obtained above.

Determine the lower t-percentile value for the following one-sided lower confidence intervals:

1. Confidence level = 95%, degrees of freedom = 20
2. Confidence level = 99%, degrees of freedom = 20
3. Compare the two t-percentile values obtained above.