Hey Guys, Anyone good with statistics? There's this homework problem that I'm working on. Any help would be greatly appreciated. The problem is: The mean selling price of new homes in Sugar Land over a year was $120,000. The population standard deviation was $28,000. A random sample of 100 new home sales from this city was taken. 1. What is the probability that the sample mean selling price was more than $116,000? 2. What is the probability that the sample mean selling price was between $118,000 and $122,000? 3. What is the probability that the sample mean selling price was between $119,000 and $121,000? 4. Suppose that, after you had done these calculations, a friend asserted that the population distribution of selling prices of new homes in this city was almost certainly not normal. How would you respond?
You should have a curve that converts standard deviation units into percentages. The values are exact and I have the table somewhere, but you should have it too. Just convert everything here to standard deviation units. For example, $116,000 is .143 Standard Deviations below the mean. Then use the chart and get the percentage that represents. Add .5 to it. Tada.
http://mathbits.com/MathBits/TISection/Statistics2/normaldistribution.htm Answer to 4. is "I'd shank him because if this distribution is not normal then I have just wasted 5 minutes of my life."
It's always; absolute (mean-x/(standard deviation)) (120000-116000)=4000 4000/28000=.143 Just always remember whether you're dealing with a smaller or bigger value then the mean, since the equation will give you the same for 116,000 and 124,000. If it's smaller then the mean then it's .143 standard deviations below the mean. If it's bigger, then it's .143 standard deviations above the mean.
youre the man--- just found that equation in the book what about when the question asks for between a price like "between 118,000 and 122,000"
i think i have it figured out northside, thanks for your help-- i will post back with the answers i find
I'm not Northside, but what did you get when you looked up the probability in the z table? Some tables are different in the way they give the probability. Your table might only give the probability (area under the curve) from the z-score to the mean. For question #1, the table may only give the probability of between $116,000 and $120,000. Therefore, you would have to add .5 to the value since the question asks for the probability for more than $116,000.
