Question

With 80% confidence, for sample proportion 0.40 and sample size 26, what is the upper confidence limit with 2 decimal places?

Answer 1

Solution :

Given that,

n = 26

= 0.40

1 - = 1 - 0.40 = 0.60

At 80% confidence level the z is ,

= 1 - 80% = 1 - 0.80 = 0.20

= 0.20

Z = Z_0.20 = 0.842

Margin of error = E = Z _{/ 2} * (( * (1 - )) / n)

= 0.842 * (((0.40 * 0.60) / 26) = 0.08

A 80 % confidence interval for population proportion p is ,

+ E

0.4+ 0.08

0.48

The 80% confidence interval for the population proportion p is : ( upper limit =  0.48)