Consider the twosided confidence interval expression x Z al

Consider the two-sided confidence interval expression x - Z alpha/2 sigma/square root n

Solution

a)

Note that

alpha/2 = (1 - confidence level)/2 =    0.01      

Thus, by table/technology,

z(alpha/2) = critical z for the confidence interval =    2.326347874 (or 2.33 by table)

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b)

Note that

alpha/2 = (1 - confidence level)/2 =    0.10      

Thus, by table/technology,

z(alpha/2) = critical z for the confidence interval =    1.281551566 (or 1.28 by table)

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c)

Note that

alpha/2 = (1 - confidence level)/2 =    0.125      

Thus, by table/technology,

z(alpha/2) = critical z for the confidence interval =    1.15034938 (or 1.15 by table)