A random sample of 20 size AA batteries for toys yield a mean of 3.27 hours with standard deviation, 1.17 hours. (a) Find the critical value, t*, for a 99% CI. t* =
.6504
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(b) Find the margin of error for a 99% CI.

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.1. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 8 pins is at least 51?

Find the zeros of each function. f(x) = 6x^2 - 7x - 20

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