Mean Family Income and Violent Crime By Avery Bishop, Brandon Miller and Julieta Cueva

Brian Heaven

Statitistics Project


What is the correlation between Mean Family Income and Violent Crime in the counties of California?


This study was conducted to determine whether there is a significant relationship between between a family’s income and the amount of violent crime in an area. Fifteen counties in the state of California were randomly selected based off of the mean family income in each county. The data found suggests that there is a weak correlation between mean family income and violent crime rate.


Crime in the United States is constantly dropping and spiking, yet prison population continues to soar. The state of California has vast ranges in income throughout their population. Although there is a stigma around poverty and high crime, the data can certainly suggest that crime rates can be similar in both areas of high and low income. With crime not being exclusive to one particular area and income level, the null hypothesis for this study is that there will be no correlation between mean family income and crime rates in California counties, and the alternative hypothesis is that there is a strong correlation between mean family income and crime rates in the counties of California.

Lurking Variables include but are not limited to Relationship Problem(s), Level of Education, and if the crime went unnoticed or wasn't reported.


Fifteen counties in the state of California were selected by creating three groups. The groupings pertain to the Mean Family Income, and were organized into goups of under fifty thousand, fifty thousand to eighty thousand, and over eighty thousand. All fifty eight counties of California were placed into one of these three income level groups. After the counties were placed into one of the groups, five counties from each group were randomly selected. For the under fifty thousand groups, Tulare, Siskiyou, Modoc, Imperial, and Yuba were the counties selected. In the fifty thousand to eighty thousand group, the counties selected were Sacramento, San Diego, Los Angeles, Fresno, and Riverside. Lastly, for over eighty thousand, Orange, Alameda, Contra Costa, Marin, and Santa Clara were selected for this study.


The data found through this study shows that there is a weak correlation between the two variables.

Screenshot of our Results

To calculate the results of this study, the LineRegTTest calculator app was used. The results were t= - 1.20, p= .249, r= -.31 and n= 15. The data suggests that at the 0.05 significance level, there is not a strong correlation between the data, therefore we fail to reject the null.


This study was created to determine the correlation between mean family income and crime rate. A study from 2008-2012 by the Bureau of Justice Statistics found that people in poor households experienced more than double the rate of violent victimization than people in high income households. Despite the study conducted from 2008-2012, the data found in this study showed that there is not a strong connection between how low or high the mean income is and the amount of crime that happens in that particular area. In the state of California, the crime rate appears to vary no matter what mean income level each county has.


To calculate the crime rate for each county, the number of violent crimes for each county was divided by the county population, and then divided by one thousand. This calculation was used to determine the crime rate per one thousand people in fifteen of California’s counties. To calculate linear regression, the mean income for each county was inputted into L1 and the crime rate was inputted into L2. Then, STAT> Tests> LinRegTTest to find the values for t, p, and r.


"List of California Locations by Income." Wikipedia. Wikimedia Foundation, 24 Sept. 2016. Web. 04 Mar. 2017.<>.

State of California, Department of Justice, Office of the Attorney General. "Open Justice." State of California Department of Justice - OpenJustice. N.p., n.d. Web. 05 Mar. 2017. <>


Created with images by Rob de Vries, - "untitled image" • Norm_Bosworth - "sandstone the wave rock" • Rob de Vries, - "untitled image" • Mark Bonica - "oil abstracts" • XoMEoX - "Abstract" • Rob de Vries, - "untitled image" • Florian Schwalsberger - "abstract." • avrene - "Red Abyss" • kalmankovats - "sunlight sunbeam vibrant"

Made with Adobe Slate

Make your words and images move.

Get Slate

Report Abuse

If you feel that this video content violates the Adobe Terms of Use, you may report this content by filling out this quick form.

To report a Copyright Violation, please follow Section 17 in the Terms of Use.