Question 1176712
mean is 4.322 %
sd is 0.226%
99% half CI is t (0.995, df=11)*s/sqrt(n)
=3.106*0.226/sqrt(12)
=0.203
the 99% interval is (4.119, 4.525) units %
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Because 4.050% is outside the interval, it is reasonable to claim the true rate has risen. We are 99% confident that the true value, whatever it is, lies within the interval.