In: Statistics and Probability
Based on historical data, your manager believes that 30% of the company's orders come from first-time customers. A random sample of 77 orders will be used to estimate the proportion of first-time-customers. What is the probability that the sample proportion is between 0.34 and 0.47?
Solution:
Given that,
n = 77
= 30% =0.30
1 - = 1 - 0.30 = 0.70
= = 0.30
= ( 1 - ) / n
= 0.30 * 0.70 / 77
= 0.0522
= 0.0522
p ( 0.34 < < 0.47 )
p ( 0.34 - 0.30 / 0.0522 ) < ( - / ) < ( 0.47 - 0.30 / 0.0522 )
p (0.04 / 0.0522 < z < 0.17 / 0.0522 )
p ( 0.77 < z < 3.26 )
p ( z < 3.26 ) - p ( z < 0.77 )
Using z table
= 0.9994 - 0.7794
= 0.2200
Probability = 0.2200