Histograms, Frequency Polygons, and Time Series Graphs · Exercise 11

The following data sets list full-time police per 100,000 citizens along with incidents of a certain crime per 100,000 citizens for the city of Detroit, Michigan, during the period from 1961 to 1973.

$$\begin{array}{cccccccc}\text{Year}& \text{1961}& \text{1962}& \text{1963}& \text{1964}& \text{1965}& \text{1966}& \text{1967}\\ \text{Police}& \text{260.35}& \text{269.8}& \text{272.04}& \text{272.96}& \text{272.51}& \text{261.34}& \text{268.89}\\ \text{Incidents}& \text{8.6}& \text{8.9}& \text{8.52}& \text{8.89}& \text{13.07}& \text{14.57}& \text{21.36}\end{array}$$

$$\begin{array}{ccccccc}\text{Year}& \text{1968}& \text{1969}& \text{1970}& \text{1971}& \text{1972}& \text{1973}\\ \text{Police}& \text{295.99}& \text{319.87}& \text{341.43}& \text{356.59}& \text{376.69}& \text{390.19}\\ \text{Incidents}& \text{28.03}& \text{31.49}& \text{37.39}& \text{46.26}& \text{47.24}& \text{52.33}\end{array}$$

(a) Construct a double time series graph using a common x-axis for both sets of data.
(b) Which variable increased the fastest? Explain.
(c) Did Detroit’s increase in police officers have an impact on the incident rate? Explain.

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Statistics · §2.2 Histograms, Frequency Polygons, and Time Series Graphs · Exercise 11