In: Statistics and Probability
A survey of 542 consumers reveals that 301 favor the new design for a product. Construct a 90% confidence interval for the true proportion of all consumers who favor the design.
Group of answer choices
0.514 < p < 0.597
0.522 < p < 0.588
0.520 < p < 0.591
0.500 < p < 0.610
0.518 < p < 0.593
Solution :
Given that,
n = 542
x = 301
Point estimate = sample proportion = = x / n = 301/542=0.555
1 - = 1-0.555 =0.445
At 90% confidence level
= 1 - 90%
= 1 - 0.90 =0.10
/2
= 0.05
Z/2
= Z0.05 = 1.645 ( Using z table )
Margin of error = E Z/2 *(( * (1 - )) / n)
= 1.645 *((0.555*0.445) /542 )
E = 0.035
A 90% confidence interval for proportion p is ,
- E < p < + E
0.555-0.035 < p < 0.555+0.035
0.520 < p < 0.591