Find the a/2 ( the area in one tail outside of the confidence interval) and the critical value z a/2 necessary to construct an 80% confidence interval.

a sample size n=99 is drawn from a population whose standard deaviation is 11 (a) find the margin of error for a confidence interval for u (population mean). round the answer to at least three decimal places  the margin of error for a 90% confidence for u (population mean) is

Suppose we are making predictions of the dependent variable y for specific values of the independent variable x using a simple linear regression model holding the confidence level constant. Let Width (C.I) = the width of the confidence interval for the average value y for a given value of x, and Width (P.I) = the width of the prediction interval for a single value y for a given value of x. Which of the following statements is true? Width (C.I) = 0.5 Width (P.I) Width (C.I) = Width (P.I) Width (C.I) > Width (P.I) Width (C.I) < Width (P.I)

A statistical study is made to compare the % of smokers in small rural towns to the overall smoking rate of the US. Of 1500 asults selected randomly from small towns it is found that 285 of them smoke. With a cofidence interval of (017, 0.21). The CDC reports that 15.1% of all American adults smoke. Does the confidence interval suggest that smoking rate is higher in small towns than in the country overall?

find the critical value Z of alpha over 2 used to construct a confidence interval of 94%

Suppose a marketing company randomly surveyed 404 households and found that in 214 of them, the woman made the majority of the purchasing decisions. Construct a 90% confidence interval for the population proportion of households where the women make the majority of the purchasing decisions.p'=α2=zα2=Margin of Error: E=We are 90% confident that the proportion of households in the population where women make the majority of purchasing decisions is between___ and ___.

Find the level of the confidence interval that has the value Za/2 = 1.28. (Round the final answer to three decimal places.)

A random sample of size 30 from a normal population yields  = 39  and s = 4.9.  The lower bound of a 95 percent confidence interval is  (Round off upto 2 decimal places).

What would be the critical value for a left-tailed test with α = 0.01? (Remember to use the z-score table)

Find the critical values x1-a/2 for a 98% confidence level and a sample size of n = 25. and α/2 1-a/2 (Round to three decimal places as needed.)