11. Calculate the appropriate critical z -value for each of the following confid

Question

11. Calculate the appropriate critical z-value for each of the following confidence levels? (a) 95% confidence level: (b) 98% confidence level: 12. Does a confidence interval for µ built from some collected sample mean get wider or narrower if: (a) the percent of desired confidence (confidence level) increases from 85% to 90%? (b) the size of the sample used to produce the confidence interval is increased? (c) the standard deviation gets larger? 11. Calculate the appropriate critical z-value for each of the following confidence levels? (a) 95% confidence level: (b) 98% confidence level: 12. Does a confidence interval for µ built from some collected sample mean get wider or narrower if: (a) the percent of desired confidence (confidence level) increases from 85% to 90%? (b) the size of the sample used to produce the confidence interval is increased? (c) the standard deviation gets larger?

Explanation / Answer

Please post question individiually. I am answering the 1st Qn:

a. 95% CI ?

1.Go to the Z tables.
2. Since 95% CI is asked , we first divide the 95% by 2 = 47.5%
3. Then add 50% to it to get 97.5%, this is cum. area
4. The Z score relating to .975 is 1.96
5. Similarly, for lower end is it -1.96

Answer is : +/- 1.96

b. 98% CI,

repeat the above exercise to get the answer as:

Answer is +/- 2.325

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