A) A random sample of 100 observations produced a sample proportion of .25. An approximate 90% confidence interval for the population proportion p is

a. 
.248 and .252 

b. 
.179 and .321 

c. 
.423 and .567 

d. 
.246 and .254 

e. 
None of the above answers are correct. 
B)
Suppose that an investigator believes that virtually all values in the population are between 38 and 70. The appropriate sample size for estimating the true population mean μ within 2 units with 95% confidence level is approximately

a. 
61 

b. 
62 

c. 
15 

d. 
16 

e. 
None of the above answers are correct. 
Solution:Given that,{:[n=100],[ hat(p)=0.25]:}confidence level =90%{:[ hat(p)=0.25],[ hat(q)=1 hat(p)],[=10.25],[=0.75]:}At 90% confidence level{:[1alpha=0.90],[alpha=10.90],[alpha=0.10],[(alpha)/(2)=0.05]:}z(alpha)/(2)=z 0.05=(1.645)/(" (vsing standard normal tabie) ")" Margin of error "{:[E=2(alpha)/(2)xxsqrt((( hat(p))( hat(q)))/(n))],[=1.645 xxsqrt(((0.25)*(0.75))/(100))],[E=0.071]:}confidence intervel for ' p '{:[ hat(p)E <= P <= hat(P)+E],[0.250.071 <= P <= 0.25+0.071],[0.179 <= P <= 0.32 ... See the full answer