A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained if he wishes the estimate to be within 4 percentage points with 95​% confidence if ​(a) he uses a previous estimate of 32​%? ​(b) he does not use any prior​ estimates?

Respuesta :

Answer:

sample size if he uses a previous estimate of 32​% is 523

sample size if he does not use any prior​ estimates is 601

Step-by-step explanation:

estimate E = 4 percentage = 0.04

confidence Cl = 95% = 0.95

previous estimate p = 32% = 0.32

q = 1 - 0.32 = 0.68

to find out

size of sample

solution

first we calculate z value for 95% confidence E = 0.04 is 1.96

from probability P(-1.96 < z < 1.96) = 0.95)

here z = 1.96

so in 1st part size of sample we know

E = z × [tex]\sqrt{pq/n}[/tex]

put all value E, z p and q and we get n

n = (z/E)² ×p×q

n = (1.96/0.04)² ×0.32×0.68

n = 523

sample size if he uses a previous estimate of 32​% is 523

now in 2nd part we take p = 0.5

so n will be

n = (z/E)² ×p×q

n = (1.96/0.04)² ×0.5×0.5

n = 601

sample size if he does not use any prior​ estimates is 601

Sample size if he uses a previous estimate of [tex]32[/tex] % is [tex]523[/tex]

Sample size if he does not use any prior​ estimates is [tex]601[/tex]

Estimate [tex]E=4[/tex], Percentage = [tex]0.04[/tex]  and Confidence [tex]CI=95[/tex] % [tex]=0.95[/tex]

Previous Estimate [tex]p=32[/tex] % [tex]=0.32[/tex]  and [tex]q = 1 - 0.32 = 0.68[/tex]

To find out  size of sample  solution first we calculate [tex]Z[/tex] value that is [tex]1.96[/tex]

from Probability,  [tex]P(-1.96 < z < 1.96) = 0.95)[/tex]

So, in first part size of sample we know

[tex]E=Z\times \sqrt{\frac{pq}{n}}\; \Rightarrow \; n=\left ( \dfrac{Z}{E} \right )^2\times p\times q\\ \\ n=\left ( \frac{1.96}{0.04} \right )^2\times 0.32\times 0.68\\ \\ n=523[/tex]

 Therefore, Sample size if he uses a previous estimate of [tex]32[/tex] % is [tex]523[/tex]

Now in second part we take [tex]p = 0.5[/tex]

[tex]E=Z\times \sqrt{\frac{pq}{n}}\; \Rightarrow \; n=\left ( \dfrac{Z}{E} \right )^2\times p\times q\\ \\ n=\left ( \frac{1.96}{0.04} \right )^2\times 0.5\times 0.5\\ \\ n=601[/tex]

Therefore, Sample size if he does not use any prior​ estimates is [tex]601[/tex]

Learn more about sample size.

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