In: Statistics and Probability
In a sample of 600 potential car buyers, 376 indicated that they would consider purchasing a hybrid gas/electric-powered car. Find and interpret the 95% confidence interval (z*=1.96) for the true population proportion of potential car buys that would consider purchasing a hybrid vehicle. Round your answer to 3 decimal places.
Solution :
Given that,
n = 600
x = 376
Point estimate = sample proportion = = x / n = 376/600=0.627
1 - = 1- 0.627 =0.373
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 (((0.627*0.373) / 600)
E = 0.039
A 95% confidence interval for population proportion p is ,
- E < p < + E
0.627-0.039 < p <0.627+ 0.039
0.588< p < 0.666
The 95% confidence interval for the population proportion p is : 0.588, 0.666