A real estate agent needs to estimate the average value of a residential property of a given area in a certain city. The agent decides to select a large random sample. (a) The agent selects a random sample of 225 properties in the area and the sample result shows an average of $200 thousand with a standard deviation $90 thousand. Find a 90% confidence interval for the real average value. (b) One year later, the agent will select a large random sample and estimate the average value again. He is willing to assume that the standard deviation of property values will remain the same as $90 thousand. He also wishes to ensure that 95% of the times, the estimated average value will be within $2 thousand of the real average. What is the minimum sample size required?
1. A real estate agent needs to estimate the average value of a residential property of a given area in a certain
city. The agent decides to select a large random sample.
(a) The agent selects a random sample of 225 properties in the area and the sample result shows an average of
$200 thousand with a standard deviation $90 thousand. Find a 90% confidence interval for the real average
value.
(b) One year later, the agent will select a large random sample and estimate the average value again. He is
willing to assume that the standard deviation of property values will remain the same as $90 thousand. He
also wishes to ensure that 95% of the times, the estimated average value will be within $2 thousand of the
real average. What is the minimum
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