In: Statistics and Probability
2. A survey of 40 individuals reveals that 19% plan to move within the next year. Find a 95% confidence interval for the proportion of people who plan to move next year. (3)
Solution :
Given that,
n = 40
Point estimate = sample proportion = =19%=0.19
1 - = 1-0.19 =0.81
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.96 ( Using z table )
Margin of error = E = Z/2 * ((( * (1 - )) / n)
= 1.96 (((0.19*0.81) /40 )
E = 0.122
A 95% confidence interval for population proportion p is ,
- E < p < + E
0.19-0.122 < p < 0.19+0.122
(0.068 , 0.312)