Whenever the population standard deviation is unknown, which distribution is used in developing an interval estimate for a population mean

The t-distribution is used.

Step-by-step explanation:

When we dont know the standard deviation of the population, we use the t-distribution(t-table).

Otherwise, the z-distribution(z-table) is used.

So the answer to this question is the t-distribution.

The Millers paddled 4,666 miles each day.  If they reduced their daily distance by half, extending their trip to twice as many days, the distance traveled by the Millers would have been the same.

Step-by-step explanation:

Given that the Miller family likes to paddle along the river, and they paddled the same distance each day throughout the course of three days, traveling a total of 14 miles, to determine how many miles did they travel each day the following calculation must be performed :

14/3 = X

4.666 = X

Thus, the Millers paddled 4,666 miles each day.

In turn, if the Millers went half their daily distance each day, but extend their trip to twice as many days, to determine how far would they travel, the following calculation must be performed:

4.666 / 2 x 6 = X

2.333 x 6 = 13.9999

Thus, the distance traveled by the Millers would have been the same.