What is the difference between confidence level and confidence interval?

1. Find the critical value that Zα/2 that corresponds to a 99% confidence level.?

• 1. Find the critical value that Zα/2 that corresponds to a 99% confidence level. (a) 1.645 (b) 1.96 (c) 2.575 (d) 2.32 2. Find the critical value that Zα/2 that corresponds to an 85% confidence level. (a) -1.44 (b) 1.04 (c) 1.85 (d) 1.44 3. In a poll of 1,000 randomly selected adults, 400 answered “yes” when asked if they planned to vote in the state election. What is the best point estimate of the population proportion of all adults who plan to vote in that election? (a) 0.040 (b) 0.004 (c) 0.600 (d) 0.400 4. Refer to question 3 above. Find the margin of error E that corresponds to a 95% confidence level for the proportion of voters who plan to vote. (a) 0.0304 (b) 0.9696 (c)0.0255 (d) 0.0399 5. The Genetics and IVF Institute conducted a clinical trial of the XSORT method designed to increase the probability of conceiving a girl. In the clinical trial 574 babies were born to parents using the XSORT method, and 525 of them were girls. What is the best point estimate of the population proportion of girls born to parents using the XSORT method? (a) .525 (b) .574 (c) .915 (d) 1.09 6. Refer to question 1. Construct a 95% confidence interval estimate of the percentage of girls born to parents using the XSORT method. (a) 0.819 < p < 0.865 (b) 0.865 < p < 0.916 (c) 0.838 < p < 0.882 (d) 0.892 < p < 0.937

• Answer:

  1) 2.575 2) The middle area is 85%. The area to the right of the middle is 15/2 = 7.5% The area to the left of the middle is 7.5% Locate 0.075 in the area and read z reversely. Zα/2 =1.44