Question 1192814
It is $19/sqrt(9), the sd/sqrt(n)=$6.33
b. z=(x-mean)/sigma/sqrt(n)=3/(19/3)=0.4739
prob. z >0.4739=0.3178
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c. This is z <-4/6.33 =-0.6319; probability of that is 0.2637
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d.Between 63 and 70 is 1- the sum of those two probabilities above, or 1-0.5815=0.4185
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e. This would be +/- 9/6.33=1.42. That probability is 1-0.8444 (the probability between them)=0.1556.
There will be slight differences in the fourth decimal place if you round the z-value. Generally, 2 places may be done, but some may want you to round the z-value only at the end.