One major reason that the two-sample t procedures are widely used is that they are

Confidence levels and P-values from the t procedures are quite accurate even if the population distribution is not exactly Normal

Step-by-step explanation:

Confidence levels and P-values from the t procedures are quite accurate even if the population distribution is not exactly Normal

there is a general rule that depicts that T is okay to use when n >30. also when the sampling method for each sample is simple random sampling and samples are independent.

6,591,024,000

Step-by-step explanation:

Minutes in 24 hours=1,440

number of seconds in 24 hours=60*1440

=86,400..

number of cars made in each second=209

number of cars made in 86,400 seconds= 18,057,600

24 hours =one day

1 year =365 days

cars made in one year =365*18,057,600

=6,591,024,000

therefore, the number of cars made in one year =

6,591,024,000