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# Normal Probability:Selling price of homes &web site visitors

Problem 1

The mean selling price of new homes in a city in 2010 was \$115,000. The population standard deviation was \$25,000. A random sample of 100 new home sales from this city was taken.

A) What is the probability that the sample mean selling price was more than \$110,000?

B) What is the probability that the sample mean selling price was between \$113,000 and \$117,000?

C) 85% of the homes sold in the city were sold for less than what amount of money?

Problem 2

According to a survey, only 15% of customers who visited the web site of a major retail store made a purchase. Random samples of size 50 are selected.

A) What proportion of the samples of size 50 will have between 20% and 30% of customers who will make a purchase after visiting the web site?

B) What is the probability that a random sample of 50 will have at least 30% of customers who will make a purchase after visiting the web site?

C) 90% of the samples of size 50 will have less than what percentage of customers who will make a purchase after visiting the web site?

#### Solution Summary

The solution provides step by step method for the calculation of probability using the Z score. Formula for the calculation and Interpretations of the results are also included.

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