Overview: To better understand statistical inference you will use sampling techniques and confidence intervals to answer questions concerning a population of single-family homes in Wake County, North Carolina. Rather than going from house to house in the county, you will make use of an online database that lists key characteristics of these homes.

Image - Mikhail Leonov used with permission through Dreamstime.com

Before you start working on this activity, click on the link below to save a copy of the Data Report Form Excel file to your computer. You'll need this form to record the information from the property listing and to do your data analysis. You can also put the answers to the questions below on the same Excel form. As a reminder, you can get Excel for free and enter your school email address. You may have to leave the "my." out of your email.

Click on the Link: Real Estate Starter Data

There are approximately 310,000 properties in the Wake County database. In the file linked above, there are 50 "random" numbers generated for you to use. In this activity, you need a sample of 30 single-family homes. There are 50 random numbers because some of the real estate properties won't be single-family residences. You can stop once you have 30 single-family homes. The first 25 single-family homes are completed for you, so you only need to find 5 more.

1. Open the website Wake County Real Estate Data. The website allows the user to search property listings based on their Real Estate Id (REID) number as well as other indicators. You will enter each ID number from your list of randomly generated numbers until you have a total of 30 single-family houses.
2. After you enter the REID number, you will be transferred to an account summary for the property listing. Click on the Buildings tab.
3. Before going any further, verify the property is a single family home. If the property is not a single family home, enter the next randomly generated number in the Account Search field to the right. Do not enter data from properties that are not listed as single family homes.
4. If the property is a single family home, record the following in the Excel file you had downloaded earlier: Real Estate ID Number - Record the number Address - Record the street address Total Value assessed - Record the amount Heated Area - Record the number Air Conditioning - Record yes or no Fireplace - Record yes or no
5. Calculate 95% and 99% confidence intervals for the Total Assessed Value, Heated Area, Air Conditioning, and Fireplaces based on your sample data. Keep in mind that these variables are not the same type. You'll need to decide which formula to use for each variable. There should be a total of 8 confidence intervals calculated, 2 for each of the 4 variables. Show your work in doing these calculations, showing which formula you are using, giving the critical value, standard error, margin of error, etc..
6. Explain what each of the confidence intervals tell you concerning the homes in Wake County. Write these explanations in full sentences! Example: We are 95% confident that the mean assessed value of all homes in Wake County is... etc.
7. Considering the confidence intervals, answer the following questions: a. By increasing the confidence level, explain how the confidence intervals were affected and why that makes sense. b. If more data was used in the sample, explain how the confidence intervals would be affected and why that makes sense.
8. Write a short report that summarizes what you discovered about the single family homes in Wake County.
9. Turn in your Excel data set along with the confidence interval calculations and answers to the questions above using this dropbox.

Note: If you are photographing your work: 1) Make sure the image isn't too small in resolution. 2) Dont tilt the camera sideways. Take the photo in portrait orientation (or "straight up")

PROPERTY DATA

REID #AddressTotal ValueHeated AreaACFP

149128 6212 RIVER LANDINGS DR$147,760.001362YesYes

33634 1429 KERSHAW DR$503,928.003503YesYes

2552 2704 KNOWLES ST$97,349.00752YesNo

195111100 DOVERSHIRE CT$346,265.002348YesYes

1823801209 TROTTER BLUFFS DR$196,455.001770YesYes

223331 1809 BETRY PL $205,512.001702YesYes

161966 215 TORREY PINES DR$1,252,725.005482YesYes

162092 104 KEITHWOOD LN$225,073.001678YesYes

147353 102 CULCROSS CT$236,650.001984YesYes

146269 603 BROAD LEAF CIR$114,830.001388YesYes

295713 2524 HIDDEN MEADOW DR$265,743.002862YesYes

89006 109 KIERNAN CHOICE $320,351.002634YesYes

2192741706 ASHBARK CT$238,192.002030YesYes

218914 8301 HOBHOUSE CIRCLE $231,391.002074YesYes

164011 105 TOLLIVER CT$337,743.003079YesYes

250499 363 SEASTONE ST$237,908.002371YesYes

194739 106 LARSKSPUR LN $295,116.001873YesYes

1341867904 SUTTERTON CT$355,379.002428YesYes

136262 1009 HARVEST MILL CT$189,806.002068YesYes

126983 2013 COUNTRYWOOD NORTH RD$411,819.002868YesYes

82591500 PERRY CURTIS RD$36,687.00952NoNo

210521 113 DEEP GAP RUN$301,433.002752YesYes

7805 906 DOROTHEA DR $361,359.001344YesNo

504711209 PARK DR$662,800.003080YesYes

205640509 MIDENHALL WAY$509,432.003045YesYes

152122

204944

73613

52093

145536

7540

135484

230306

161244

189029

48956

1696

93796

194386

19552

186879

90233

117923

165010

32669

256848

226365

147863

257792

257339