Bon Air Housing Values: A Second Look at Overall Values With Better Software

This is the third in a series of a look at housing values in the Bon Air Neighborhood as defined by the following boundaries: Furman Blvd on the east, Hikes Lane on the south, Bardstown Road on the East, and the Watterson Expressway/Taylorsville Rd on the North.

I confess that as I have written this post, it is the kind of stuff that is more egghead and boring and I hope that I do not sound too much like that weird guy you hated because he was actually excited about statistics class and he wrecked the bell curve.

The database for this research was created from the Jefferson County Property Valuation Administrator (PVA) website and the Lojic.org website.  Both have similar data, but the PVA site could be pasted into an Excel file. The database was compiled between February 2019 and December 2019. The information was subject to some change based on property sales and re-evaluations.

The statistical software that is being used for the analysis is JASP which is an open source program created by the University of Amsterdam.

The dataset was adjusted to eliminate non-housing properties that reduced the data set from 1995 cases (used in the last post) down to 1975 cases (or properties with houses on them).

An initial run of descriptive statistics was run with the following results:

Statistical Table with Min and Max

Descriptive Statistics
		VALUE
Valid		1975
Missing		13
Mean		138316.319
Median		135000.000
Mode		155000.000
Std. Deviation		30185.350
Skewness		1.555
Std. Error of Skewness		0.055
Kurtosis		11.110
Std. Error of Kurtosis		0.110
Range		468400.000
Minimum		2110.000
Maximum		470510.000
25th percentile		118650.000
50th percentile		135000.000
75th percentile		153900.000

The most valuable numbers out of this table are the Mean (average) and Median (middle point of the numbers).  For Bon Air as a whole the mean or average home value was $138,216.  The Median was 135,000.  This initially would say that matters are an even deal, however, when you look at graphics--especially the bar graph at the beginning of this post, it is very skewed or distorted. to the higher values with a value of 1.555 (should be 1 or less).

The skewness makes some sense when you see a range of $470510 (distance between highest and lowest number.  The maximum home value was $470510 and the lowest privately held property is $2110.  The highest valued property is a bed and breakfast and the lowest value is a piece of that triangle/cemetery at Bon Air and Goldsmith Lane (that one crooked part).

 So, an adjustment was made by taking out the highest and lowest properties and re-running the analysis. Here are the results

Adjusted Descriptive Statistics

Descriptive Statistics
		VALUE
Valid		1973
Missing		13
Mean		138216.984
Median		135000.000
Mode		155000.000
Std. Deviation		29098.145
Skewness		1.045
Std. Error of Skewness		0.055
Kurtosis		4.487
Std. Error of Kurtosis		0.110
Range		315620.000
Minimum		5000.000
Maximum		320620.000
Sum		2.727e +8

Cutting out the highest and lowest value did fix the skewness or distortion and it was significant that the mean (average) median (middle) values stayed virtually the same. Of course the range was shortened down to $315,620 with a high value of $320,620 and a vacant property value of $5000.

At this point that silly term "standard deviation" might be of some value.  It is a group of numbers that cluster around the average or mean.   Before adjustment the standard deviation was  $30,185.  After adjustment the standard deviation was $29,098.  It changed less than $1000.  Before I lose anyone else, let's look at a graph called a "Box Plot."

The box plot is valuable in illustrating the standard deviation in this case. It shows the majority of the housing values cluster between approximately $130,000 and $170,000.  That is the middle of the pack.  If we were to be precise, the central tendency of the housing values in the neighborhood are between $149,549 and $120451. The cluster appears to be just bigger than the standard deviation. There are a few outliers that still skew the data but not as much.

The next planned post in this series will be about the values of houses in the different zones.  It might explain some of the overall housing values.

We in the Bon Air Neighborhood Association are about doing things that improve our housing values and that includes our current arts development initiative.  We hope that you will join us as a member if you are not already one.  Our next meeting is tomorrow, Monday February 10, 2020 at 6:30 pm in the Bon Air Library on the "Boulevard."