In: Statistics and Probability
Based on historical data, your manager believes that 31% of the company's orders come from first-time customers. A random sample of 187 orders will be used to estimate the proportion of first-time-customers. What is the probability that the sample proportion is greater than than 0.23?
Solution:
Given that,
n = 487
=31% =0.31
1 - = 1 - 0.31 = 0.69
= = 0.31
= ( 1 - ) / n
= 0.31 * 0.69 / 187
= 0.0338
= 0.0338
P( > 0.23 )
= 1 - P ( < 0.23 )
= 1 - P ( - / ) < ( 0.23 - 031 / 0.0338 )
= 1 - P ( z < -0.08 / 0.0338 )
= 1 - P ( z < -2.37 )
Using z table
= 1 - 0.0089
= 0.9911
Probability = 0.9911