The standard deviation of a probability distribution table is 26.6 and the mean is 674.0. during an event, you receive the result of 622.3. determine whether this value is considered usual or unusual and tell why.
a.
unusual, because the result is less than the minimum usual value.
b.
usual, because the result is less than the minimum usual value.
c.
usual, because the result is within the range of the minimum and maximum usual values.
d.
unusual, because the result is within the range of the minimum and maximum usual values.

Multiply. write your answer in simplest form. 3/8 x 5/7

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.