Reference no: EM13324392

Analysis of Interrupted Time Series Data

In 1974, the United States instituted a national speed limit of 55 miles per hour (mph), a move that generated a great deal of controversy. Proponents of the lower speed limit managed to avoid repeal of this national speed limit by effectively arguing that driving at 55 mph significantly reduced the number of traffic fatalities on U.S. highways. The argument was based on the fact that the total number of traffic fatalities dropped from 55,511 in 1973 to only 46,402 in 1974. Because people have questioned the validity of this argument, you are going to examine more rigorously the hypothesis that the reduction in fatalities was due to the institution of the 55 mph speed limit.

Procedure. Since the change to a 55 mph speed limit occurred a number of years ago, you must use archival data in your study. The U. S. government routinely makes available a wide variety of data on the U.S. population. Most public and private libraries either own or would be able to get the national or state statistics you need. Here is the data you would obtain for the present research question:

Table 1: Annual Traffic Fatalities on U.S. Highways

Year Number of fatalities

1966 53,041

1967 52,924

1968 55,200

1969 55,791

1970 54,633

1971 52,660

1972 56,278

1973 55,511

1974 46,402

1975 45,853

1976 47,038

1977 49,510

1978 50,226

Source: U.S. National Center for Health Statistics, Vital Statistics of the United States, annual.

One process of policy implementation decision is the rational comprehensive decision making process. Optimum decisions are the goal. While most of the literature and focus is on economic analysis of optimality, we also need to consider social optimality. Part of that process is through empirical analysis of data and determining its validity. Our knowledge of research designs can be a valuable tool. The purpose of this case analysis is to use those tools.

The hypothesis for this policy implementation analysis is the reduction in fatalities was due to the institution of the 55 mph speed limit. Using about 1000 words (three pages of discussion) and at least 3 scholarly references (one can be the text), review this case and respond to the questions:

What kind of threats to internal validity do these events represent?

Is this policy effective? Does the increasing number of fatalities after 1974 have any implications for the effectiveness of the speed limit intervention?

What is/are one or more of the rival explanations?

What would be at least one social cost of this policy? How is it defined and measured?

What decision making theory was used? What theory should have been used?

As a final paragraph, conclude how this case discussion can assist public administrator's decision making in their role as implementing policy.