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

The following data sets list full time police per 100,000 citizens along with homicides per 100,000 citizens for a city during the period from 1961 to 1973.

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

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

(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 the city's increase in police officers have an impact on the murder rate? Explain.

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

OpenStax, Introductory Statistics 2e · §2.2 Histograms, Frequency Polygons, and Time Series Graphs · Exercise 11