Four hundred million as a standard number
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Can someone check if i did this right since i really want to make sure it’s correct. if you do you so much

Aquadratic equation in standard from is written ax^2= bx+c, where a, b and c are real numbers and a is not zero?

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.