Question

Based on historical data, your manager believes that 34% of the company's orders come from first-time customers. A random sample of 71 orders will be used to estimate the proportion of first-time-customers. What is the probability that the sample proportion is less than 0.32?

Note: You should carefully round any z-values you calculate to 4 decimal places to match wamap's approach and calculations.

Answer =0.3555 was wrong

B.Based on historical data, your manager believes that 32% of the company's orders come from first-time customers. A random sample of 138 orders will be used to estimate the proportion of first-time-customers. What is the probability that the sample proportion is between 0.21 and 0.35?

Note: You should carefully round any z-values you calculate to 4 decimal places to match wamap's approach and calculations.

Answer = 0.7736 was the wrong answer (Enter your answer as a number accurate to 4 decimal places.)

C.You want to obtain a sample to estimate a population proportion. At this point in time, you have no reasonable estimate for the population proportion. You would like to be 90% confident that you esimate is within 2.5% of the true population proportion. How large of a sample size is required?

n =
Do not round mid-calculation. However, use a critical value accurate to three decimal places.

Answer 1

A.

Given information:

Standard deviation of the proportion is:

The z-score for will be:

The probability that the sample proportion is less than 0.32 is

Excel function used for probability is "=NORMSDIST(-0.3559)"

(B)

Given information:

Standard deviation of the proportion is:

The z-score for will be:

The z-score for will be:

The probability that the sample proportion is between 0.21 and 0.35 is

C)