Question

B) How many voters should I survey to ensure a 3% margin of error with a confidence level at 95%?

C)  The senator claims that employment numbers have made gains by 8 points. You checked 20 agencies and found a mean rise of 7.8 points with st.dev. of 2.3 points. Use a 90% Confidence Interval to determine if you believe the senator's claim.

D) We collected the following data from graduates from SPC. The values are starting salaries of the first job they got after graduation in thousands.

43, 18, 34, 52, 40, 34, 47, 35

Find a 80% Confidence Interval for the population mean salary for SPC graduates.    Round answers to the nearest tenth

lower bound (in thousands)

upper bound (in thousands)

Answer 1

B)

here margin of error E =	0.030
for95% CI crtiical Z          =	1.960
estimated proportion=p=	0.500
required sample size n =	p*(1-p)*(z/E)2=	1068.00

c)

as our interval contains 8 as a plausible population mean value ; we can not reject the claim made by  senator

c)

from above lower bound =32.7

upper bound =43.0