A family is relocating from St. Louis, Missouri, to California. Due to an increasing inventory of houses in St. Louis, it is taking longer than before to sell a house. The wife is concerned and wants to know when it is optimal to put their house on the market. Her realtor friend informs them that the last 18 houses that sold in their neighborhood took an average time of 100 days to sell. The realtor also tells them that based on her prior experience, the population standard deviation is 20 days. (You may find it useful to reference the z table.)

a. What assumption regarding the population is necessary for making an interval estimate for the population mean?

multiple choice
Assume that the central limit theorem applies.
Assume that the population has a normal distribution.

b. Construct the 99% confidence interval for the mean sale time for all homes in the neighborhood. (Round final answer to 2 decimal places.)

The CI is exact for the normal populations and for small samples the z-interval method should be used in a situation where the variable is normally distributed.

b. Confidence interval:

CI=Sample mean±z-score×Standard deviation/√Size of the sample

CI=100-2.576×20/√18, 100+2.576×20/√18

CI=100-12.143, 100+12.143

CI=87.857, 112.143

Therefore the 99% Confidence interval is 87.857, 112.143.

Learn more about Confidence interval here:https://brainly.com/question/15712887

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