Question

Homicide and suicide are both intentional means of ending a life. However, the reason for committing a homicide is different from that for suicide and we might expect homicide and suicide rates to be uncorrelated. On the other hand, both can involve some degree of violence, so perhaps we might expect some level of correlation in the rates. The data from 2008–2011 for 26counties in Ohio are shown in the table. Rates are per 100,000 people.

County	Homicide rate	Suicide rate	County	Homicide rate	Suicide rate
Allen	3.8	9.9	Lorain	3.6	15.6
Ashtabula	2.8	15.5	Lucas	7.6	12.8
Butler	2.7	12.8	Mahoning	10.6	11.4
Clermont	1.0	16.0	Medina	1.0	10.0
Clark	5.4	13.6	Miami	1.0	9.6
Columiana	3.4	15.2	Montgomery	9.5	15.5
Cuyhoga	10.0	9.8	Portage	1.6	11.9
Delaware	1.0	8.2	Stark	4.8	13.0
Franklin	8.8	11.3	Summit	4.9	11.5
Greene	2.7	11.3	Trumbull	6.8	16.1
Hamilton	9.2	10.7	Warren	1.0	9.6
Lake	1.8	12.9	Wayne	1.0	10.8
Licking	4.0	13.2	Wood	1.0	8.4

To access the complete data set, click the link for your preferred software format:

Excel  Minitab  JMP  SPSS TI  R  Mac-TXT   PC-TXT  CSV CrunchIt!

(a) Make a scatterplot that shows how suicide rate can be predicted from homicide rate. There is a weak linear relationship, with correlation ?=0.17.

Each of the scatterplots in the choices has a relationship fitted to the plot. Select the plot that corresponds with the correlation of 0.17.

(b) Find the least‑squares regression line for predicting suicide rate from homicide rate, ?+?×(homicide). (Enter your answers rounded to three decimal places.)

?=

?=

(c) Explain in words what the slope of the regression line tells us.

The slope means that for every additional suicide (per 100,000 people) , there is an average increase of 0.126 homicide (per 100,000 people) in these Ohio counties.

The slope means that for every additional homicide (per 100,000 people), there is an average decrease of 0.126 suicide (per 100,000 people) in these Ohio counties.

The slope means that for every additional homicide (per 100,000 people), there is an average decrease of 11.640 suicides (per 100,000 people) in these Ohio counties.

The slope means that for every additional homicide (per 100,000 people), there is an average increase of 0.126 suicide (per 100,000 people) in these Ohio counties.

The slope means that for every additional homicide (per 100,000 people), there is an average increase of 11.640 suicides (per 100,000 people) in these Ohio counties.

(d) Another Ohio county has a homicide rate of 8.0 per 100,000 people. What is the county’s predicted suicide rate? (Enter your answer rounded to three decimal places.)

Predicted suicide rate:

Answer 1

a)

b)

Using Excel

data -> data analysis -> regression

a = 11.640

b = 0.126

y^ = 11.640 + 0.126 * x

c)

option D)

The slope means that for every additional homicide (per 100,000 people), there is an average increase of 0.126 suicide (per 100,000 people) in these Ohio counties.

d)

y^ = 11.640 + 0.126 * x

= 11.640 + 0.126 *8

= 12.648

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